Checking the results

(24.89 )(4.2 )( 8.33 ) + ( 7.106 )(2.6 )( 8.33 ) + (6 )( 7.0 ) + (62 )( 8.6 ) ( 100 )( 16 ) (871 ) + ( 154 ) + (42 ) + (533 ) 1600 1600 1600 EXAMPLE 2 (Unweighted Muds) - An equation for calculating either the volume percent low gravity solids or mud weight of an unweighted freshwater fluid is presented below 1. Using the above equation, determine the volume percent solids if the density of the mud is 10.0 lb gal and all solids are low gravity solids having a specific gravity of 2.6. 2. If...

System Conversion Maintenance Conversion

These muds generally present the same problems for conversion and maintenance as Saturated Salt Muds. Many of the problems associated with Saltwater Muds, particularly seawater muds, are due to the high concentrations of total hardness. Magnesium ion hardness (magnesium carbonate) is relatively soluble therefore, treating with soda ash for reduction of total hardness in seawater is not effective. Magnesium is however, insoluble at a pH of 10 therefore, caustic soda is effective in removing...

Pre Displacement Steps

Run bit and dual or tandem scrapers. 2. Circulate and condition mud. Reduce funnel viscosity as much as possible while maintaining sufficient rheological properties to clean hole and prevent settling of solids. Maintain critical annular velocity to assure that liner tops are thoroughly cleaned prior to displacement. 3. Rig up equipment for displacement of completion fluid. All tanks, circulating lines, and pumps to be used in the displacement should be cleared of residual mud. 4. Insure...

System Conversion Maintenance

A procedure for converting to gyp mud is similar to the lime muds however, the source of calcium is gypsum instead of lime. Native or lightly-treated freshwater low pH muds are preferred for conversion however, any water-based mud can be converted to a gyp mud. If high pH or lime muds are to be converted, more water dilution will be required to lower solids and more gypsum will be required to control alkalinity. Caustic soda is usually not required in this instance. A typical breakover from a...

Remedial Measures

When induced loss of circulation occurs, addition of loss circulation materials is not usually very effective. This is particularly true if the mud density is high, 14 lb gal or greater. Fine loss circulation material which does not adsorb a lot of water should be used in weighted mud. Recommended procedures are Monitor fluid level in the annulus (the reduction in pressure due to cessation of fluid flow may be sufficient to stabilize a minor loss.) If the fluid level is down, fill the hole with...

Minor Functions

Minor functions of a drilling fluid include Cool and Lubricate the Bit and Drill String Transmit Hydraulic Horsepower to Bit Provide Medium for Wireline Logging Assist in the Gathering of Subsurface Geological Data and Formation Evaluation Drilling fluid buoyancy supports part of the weight of the drill string or casing. The buoyancy factor is used to relate the density of the mud displaced to the density of the material in the tubulars therefore, any increase in mud density results in an...

Oil Mud Treatment

For added protection of the drill string in an H2S environment, an oil-based mud is recommended. The main advantage of a continuous oil phase fluid for drilling acid gas-bearing formations is the prevention of the various types of corrosion listed. Corrosion prevention is mostly due to the oil phase fluid eliminating one of the factors essential for completion of the electrochemical reaction necessary for corrosion to occur. The oil also forms a protective oil film on the drill pipe which is...

Chemicallbbbl

The hourly additions of barite and water were calculated to be Barite 4749 lb hr Water 24.4 bbl hr The consumption of the other materials will be based on the addition of 29 bbl of new mud volume per hour at the concentrations stated above. For the purpose of this exercise, the assumption was made that the solids contributed by bentonite and barite which are not lost from a system due to filtration or seepage were deposited as wall cake, and therefore removed from the system. It must be...

Principal Additives of KOHLime Muds

Principal Additives of KOH-Lime Muds Bentonite - Bentonite is added for viscosity and filtration control. Filtration control is created by the deflocculating action of lignosulfonate deflocculants on bentonite. Bentonite is prehydrated before being added. Lignosulfonate - Lignosulfonate is added as a deflocculant to control rheology and provide some filtration control. Lime - Lime is added to provide pH and a source of calcium. It is also added to control the PM and stabilize rheological...

Principles of Mechanical Solids Control

The basic principles of mechanical solids control are Processing in Sequence - Mud flow from the well and onward through solids control equipment must be in the proper sequence to remove the largest particles first. Total Flow Processing - All of the mud must pass through all solids removal equipment (except the centrifuge) at least once per circulation. No Bypassing - The solids removal devices (primarily the shale shaker) should not be bypassed. Chemical-Mechanical Separation -...

Weighted and Unweighted Muds Retort Data Required

Calculate the corrected solids volume percent, VCSOL, from the corrected retort water volume percent, VCW, and retort oil volume percent, VO, using the equation below Calculate the average density of all solids, rAVG, with the equation below, using Vcsol and VCW and Vo, plus the calculated rCW and the assumed (or measured) r0. The volume percent of low-gravity and high-gravity solids can be found from the rAVG, but we must assign values for the rLGS and rHGS. Usually we assume 2.6 for rLGS...

Correction of the density of the Water

Based on chloride ion analysis of mud filtrate and assuming that the salt is only NaCl, the density of the mud's water phase can be calculated. The equation for calculating NaCl brine density (rcw) is pCW 1 + (194 x 10-6)(CI-)095 g cm3 Table 3 Volume of Salt (NaCl) in the Water Phase of the Mud (Calculated From Chloride Analysis) * VCW is volume expansion due to dissolved sodium chloride. ** PCW is density increase due to dissolved sodium chloride. Table 3 can also be used to obtain corrected...

Environmental Impact and Safety

Minimizing the environmental impact of a drilling operation as well as safety considerations both directly affect the choice of drilling fluid additives and drilling fluid systems. Products that have been used in the past may no longer be acceptable. As more environmental laws are enacted and new safety rules applied, the choices of additives and fluid systems must also be reevaluated. To meet the challenge of a changing environment, product knowledge and product testing become essential tools...

Sequence of Solids Control Devices

When planning a well, it is important to take into account the type and size of solids likely to be encountered and whether or not weighting materials will be needed. These factors will determine the solids control equipment needed on the rig. The number and kinds of mechanical devices and how each is controlled during use will depend mostly on whether the mud is weighted or unweighted. It may be necessary to modify the tank arrangement and the rig solids control equipment - rather than accept...

Mud Volume in Pits

With bit on bottom, what is the volume of mud in the pits a. bbl (30 ft)(12 ft)(7 ft)' . 5.6146 ft3 bbl . Note Total Pit Capacity is 1731 bbl and Total Mud Volume is 1346 bbl. Pump Make, y4770A,ifl . Assumed Model jf> Efl. y Production or Liner Set (ffl - Ft.

Principal Additives of KOHLignite Muds

Table 36 lists principal additives for KOH-Lignite Muds. The muds are very similar to freshwater lignite-based muds in their composition and maintenance except for using caustic potash (KOH) rather than caustic soda (NaOH) for pH and alkalinity control. Table 36 lists principal additives for KOH-Lignite Muds. The muds are very similar to freshwater lignite-based muds in their composition and maintenance except for using caustic potash (KOH) rather than caustic soda (NaOH) for pH and alkalinity...

Factors Causing Shale Instability

Tectonically stressed shales Abnormally pressured shales Erosion due to high annular velocities Drill string whipping, knocking shale off the wall of the hole While tripping, the drill string dislodges shale, either by direct contact or swabbing action. Dissolving salt within the formation Mud filtrate or whole mud invasion of the formation is mechanical. The subsequent effect is chemical. Annular pressure losses in excess of 50 psi 1000 ft. This can cause wellbore erosion and instability even...

Polymer Chemistry Introduction

A polymer is a large molecule composed of a relatively small molecules called monomers (8 units) bonded together. The molecular weight of polymers range from a few thousand to several million molecular weight units. Polymers can have thousands of repeating units. The lower molecular weight polymers serve as deflocculants whereas, the high molecular weight molecules serve as viscosifiers and flocculants. The two major mechanisms for manufacturing polymers are condensation, which alters the...

Corrosion Control

Corrosion control in completion fluids is important to protect tubular goods and equipment. In sodium chloride, potassium chloride, and calcium chloride brines (and fluids based on these brines) corrosion control is relatively simple. Corrosion can be limited by controlling the fluid pH at the neutral or alkaline level, and treating out dissolved oxygen. In severe environments such as high temperature or contamination with acid gases, the addition of filming amines can limit corrosion to...

Brine Formulations

11.7 to 14.2 10.7 to 15.1 11.7 to 15.1 14.4 to 15.1 14.3 to 15.6 14.3 to 15.6 15.0 to 19.2 15.0 to 19.2 15.0 to 19.2 14.6 to 19.2 15.0 to 19.2 Crystallization Point (LCTD) F (Experimental Data) 15 to 81 45 to 68 45 to 67 55 to 59 45 to 52 39 to 64 -15 to 39 30 to 40 -30 to 15 -18 to 15 -15 to 15 -11 to 15 -2 to 20 -5 to 32 1 to 41 4 to 50 7 to 55 -58 to 68 45 to 68 -6 to 69 10 to 40 10 to 20 -8 to 28 Saturation Crystallization Temp, F (OSCA Tech. Manual

Size of Solids

Size of solids in a mud can be anything from the largest chunk that can be pumped up the annulus to clay platelets and chemical precipitates, both so small that an electron-beam microscope is needed to see them. The API has designated size ranges for particulate material in drilling muds. Sand is defined as particles larger than 74 microns (200 mesh). Particles in the 2 to 74 micron range are called silt. API barite and API hematite have size specifications set by API Spec. 13A (see Table 4)....

Preparation of Oil Base Plugs

Plug slurries can be prepared with oil and barite. A certain sequence of mixing of products is desirable for optimum performance. Always mix the wetting agent with the oil thoroughly before adding the weight material. This will aid in keeping the slurry pumpable and tie up any stray water that may be present. High density slurries settle more slowly than low density slurries because of the high solids concentration and gel strengths. Therefore, the lowest appropriate weight should be chosen,...

Bridging and Fluid Loss Agents

In the event the packer fluid comes into contact with the formation, some filtration control is necessary. This can be a particular problem with the clear brines since they do not have the solids base which forms the filter cake in conventional fluids. While polymers alone can provide substantial filtration control, it is frequently necessary to add a material to serve as a bridging agent to aid in plugging permeable formations. Graded calcium carbonate is frequently used in this application....

Saltwater Muds

Saltwater muds are often prepared from fresh water or bentonite-water muds. These muds normally contain low solids concentrations, have low densities, have minimal chemical treatment, and possess low viscosities and high fluid losses. Saltwater muds may be prepared intentionally with salt to drill troublesome shale sections. They are used as an inhibitive mud to decrease dispersion and viscosity build-up from drilled solids. These muds may range from approximately 25,000 mg L salt up to nearly...

Acid Gases

Carbon dioxide (CO2) and hydrogen sulfide (H2S) are often constituents of natural gas. Both form weak acid solutions in water which cause the clays to flocculate and may increase the viscosifying effect of polymers. Formations that contain H2S as well as CO2 can be drilled safely with water-based fluids provided the formation pressures are contained by a hydrostatic pressure greater than the pore pressure. However, proper control of the mud properties is of lesser importance than the safety of...

Volume of Lignite

4800 3 of lignite 9 15 bbl 52479 to b lr-n. Therefore, the volume of barite and water can be calculated by subtracting the volumes of bentonite, caustic and lignite from the required volume of 1200 bbl. 1200 bbl - 45.84 bbl 154.16 bbl (volumes of barite and water) The total known volume of all materials (EXCEPT barite and water) is 45.84 bbl. Then, (1154.16 - x) Volume of water Representing the problem in terms of a material balance equation V1D1 + V2D2 + V3D3 + V4D4 + V5D5 + V6D6 VfDf CMC +...

Oil Based Fluids

A primary use of oil-based fluids is to drill troublesome shales and to improve hole stability. They are also applicable in drilling highly deviated holes because of their high degree of lubricity and ability to prevent hydration of clays. They may also be selected for special applications such as high temperature high pressure wells, minimizing formation damage, and native-state coring. Another reason for choosing oil-based fluids is that they are resistant to contaminants such as anhydrite,...

Filtration Control

Starches, CMCs, PACs, and hydrolyzed polyacrylates are effective filtration control agents. Filtration control may be provided due to a physical plugging action by the polymer or by viscosifying the liquid phase of the drilling fluid. Anionic polymers control filtration by viscosifying the water phase to restrict fluid flow through the filter cake. Nonionic materials such as the starches, some anionic materials such as PAC and CMC, work by hydrating and swelling and physically plugging pores in...

Sodium

Common Chemical Symbols Cations Anions Common Chemical Symbols Cations Anions A list of the elements, symbols and atomic weights most often used in drilling fluid chemistry are found in Table 1. A compound is a substance composed of two or more elements. Table salt, for example, is a compound which is made up of an equal number of sodium and chlorine atoms. A molecule is the smallest particle of a compound which retains the composition and properties of that compound. A molecule of salt...

Troubleshooting and Contamination KOHLignite Muds

KOH-Lignite Muds are treated in the same manner as are the Lignite Lignosulfonate (Deflocculated) Muds. Table 39 lists contaminants, indicators, and treating strategies. Contaminant Treating of KOH-Lignite Muds Contaminant Treating of KOH-Lignite Muds Increasing retort solids, PV, YP, and gels. Thick mud on bot-toms-up after trips. Increased treating concentrations of additives. Major dilution. Improve solids removal. Centrifuge mud. Well flow. Increasing funnel viscosity, chlorides, YP, fluid...

Temperature

Increased temperature usually increases filtration rates by reducing the viscosity of the liquid phase, providing all other factors remain constant. Figure21 is a graph used to convert API fluid loss taken at any mud temperature to the theoretical API fluid loss value at 300 F if the pressure for both tests is the same. For example, if fluid loss at 140 F is 3.0 cm3, then multiplying by the constant 1.6 gives the theoretical value 4.8 cm3 at 300 F. The effect on fluid loss due to temperature...

Stuck Pipe Introduction

Stuck pipe during the drilling operation can occur for a variety of reasons such as hole collapse, inadequate hole cleaning, pulling the pipe into an underguage hole or by differential sticking. Stuck pipe from differential sticking, unlike the others described, usually can not be removed by working the pipe free. Differential stuck pipe usually requires the spotting of specialized fluids across the zone that the pipe is stuck to aid in freeing the pipe. If the spotting fluid is not successful,...

Typical Properties for High Temperature Deflocculated Thermadril Muds

Typical Properties of THERMA-DRIL Mud PYRO-DRIL is a high-temperature mud system sold by Milpark. This system uses a MILTEMP, a sulfonated, styrene maleic anhydride, as a high-temperature deflocculant. PYRO-TROL is an acryla-mide-acrylmido methyl propane sulfonic acid. This material is used as a high-temperature filtration control agent. PYRO-VIS is a sugar beet extract and is used to provide carrying capacity without addition of bentonite. KEM-SEAL, an acrylate-acrylamide compound, provides...

Oilin Water Emulsion for Gun Perforating

A solids-free emulsion, specifically for use when gun perforating, typically consists of 40 oil emulsified in sodium chloride, potassium chloride or calcium chloride brine. The oil phase is either kerosene or diesel, but may contain other types of refined oils. To minimize cost, emulsion slugs are pumped into the well and spotted opposite the interval to be perforated, the density having been previously adjusted so that it does not migrate in the wellbore. Field results show that oil-in-water...

Hydrogen Sulfide Corrosion Sour Corrosion

Hydrogen sulfide is sometimes associated with a gas kick or bleed-in. Other sources are makeup waters and microorganisms. Although hydrogen sulfide is relatively noncorrosive in the absence of moisture, the gas becomes corrosive if moisture is present. In the presence of CO2 or O2 and water, hydrogen sulfide becomes severely corrosive due to the driving voltage increase of the corrosion cell. Normally, when H2S corrosion is a severe problem, one of these other gases is present. The chemical...

Mixing Two Fluids

Mixing two fluids to achieve specific results is another application for material balance concepts. Simple equations can be utilized for calculating desired parameters. The following examples should help to clarify and demonstrate the use of the material balance approach. EXAMPLE 1 - A circulating system of 1000 bbl has a density of 12.0 lb gal. There are 300 bbl of 10.0 lb gal mud in storage on the rig site. How many barrels of 10.0 lb gal mud are needed to reduce the fluid density to 11.6 lb...

Carbon Dioxide Corrosion Sweet Corrosion

Sweet corrosion, as noted in production language, is attributed to carbon dioxide which occurs as a gas kick, or slow bleed-in of gas while drilling. As used here, sweet corrosion refers to a condition where no iron sulfide corrosion product occurs from a result of sour (H2S) type corrosion. Other sources of CO2 can be from the atmosphere entrapped in the mud at the surface and circulated down-hole or existing in formation waters as HCO3- or CO3 . Carbon dioxide can intrude into the borehole...

Induced Lost Circulation

Induced lost circulation is the result of an excessive overbalanced condition, where the formation is unable to withstand the effective load imposed upon it by the drilling fluid. Excessive drilling fluid density is the most common cause of this condition. Excessive drilling fluid density can be the result of inadequate or inaccurate well planning (pore pressure and fracture gradient prediction), poor or nonexistent solids control, or can be the result of poor rheology or circulating system...

Table Contd Cuttings and Discharge for Federal Outer Continental Shelf

ALASKA REGION X COOK INLET FINAL 10 86 CALIFORNIA (REGION IX) S. CALIFORNIA PROPOSED 9 85 GULF OF MEXICO REGION IV & VI FINAL 7 86 Mercury 1 mg kg Cadmium 3 mg kg Content of Barite Mercury 1 mg kg Cadmium 2 mg kg Based on barite used in each mud system. Mercury 1 mg kg Cadmium 1 mg kg Based on dry weight in the whole mud. Other Prohibited Mud Components (BAT) No discharge of Halogenated phenois Trisodium Nitriloacetic acid Sodium chromate Sodium dischromate Minimum usage allowed for...

Troubleshooting and Contamination Lime Muds

Chlorides and temperature are by far the most serious contaminants in lime muds. Table 11 lists common contaminants, indicators of contamination and treating strategies as well as some troubleshooting practices. Increasing retort solids, PV, 10-minute gel strength, MBT. Major dilution. Improve solids removal. Centrifuge mud. Increasing chlorides, Marsh funnel viscosity, yield point, gel strengths, fluid loss. Decreasing Increase density to kill flow. Dilute with freshwater. Add deflocculant,...

Shearing of PHPA Muds Cutting Down on Problems

Problems in the field - fish eyes, excessive viscosities, extensive mixing times and coating, and or plugging of shaker screens - often arise when attempting to mix some types of dry (powdered) PHPA through conventional mixing hoppers. A mixing and shearing system which minimizes these problems consists of a Flo Trend Jet Shear Mixer coupled to an Echols Homogenizer, which is capable of preparing a pre-mix of 3-6 lb bbl PHPA in a 50,000 mg L chloride brine. This concentrate can be added to the...

Old Fluid Weight Material

Substitute the product density and volume for each term in the equation. Since it is not known how much barite will be needed, the volume of barite is represented by (x). The volume of the 10.0 lb gal fluid is equal to the Old Fluid volume plus the volume of barite added. Thus the New Fluid volume equals 500 + x. (500 bbl) (9.5 lb gal) + (x) (35.0 lb gal) (500 bbl + x) (10.0 lb gal) (V )(MW ) + ( Vwm)( Dwm) (500)(9.5) + (35.0)( x) 4750 + 35x 25.5x x 500 + x 500 + 10 510 bbl of new fluid It is...

Incineration

Thermal systems can be installed on a drilling platform or placed at a convenient onshore site. These units generate air emissions in the form of partially combusted hydrocarbon particulates. The equip- ment is large, complicated, expensive and requires a central treatment facility to be cost effective. Incineration should be conducted with appropriate permits which specify the type of solid wastes to be incinerated. In addition, air pollution regulatory agency approval is required for this...

Laminar Flow

Laminar flow occurs when the individual flow layers (laminae) slide past each other with a minimum of mixing. Figure 1 demonstrates laminar flow in an annulus. Generally, laminar flow is the preferred annulus flow profile because it results in less pressure loss and reduces hole erosion. To achieve effi cient cuttings transport in laminar flow, the fluid rheology should be tailored to give a flat velocity profile, with a small n value for power-law fluid. This avoids excessive cuttings slip...

Filtration Measurement

One objective in the measurement of filtration rate is to simulate downhole conditions. Because conditions change so rapidly and frequently it is impossible to duplicate actual conditions downhole, filtration tests have been designed to produce relative measurements which are standardized and accepted in the oil industry. The tests which are made under static conditions include 1 the low temperature-low pressure test, or API fluid loss test, 2 the high temperature-high pressure test, and 3 the...

Gas Solubility in Oil Muds

Gas solubility in oil muds is many times greater than in water muds. Gas kick will remain for the most part at the point of entry and will not migrate up the hole like in a water mud. When circulating kick out, gas remains in solution and little if any gain in pit level or casing pressure is noted. When the gas comes out of solution, a rapid increase in pit level and casing pressure will be observed. Gas solubility is a function in the amount of the oil phase, and, once saturation is reached,...

Typical Properties of Lime Muds

Typically, lime muds have low viscosity and gel strengths and are rheologically stable when subjected to contaminants such as gyp, anhydrite, cement or carbonates as compared to low pH freshwater muds. Table 7 lists typical properties for a 10 lb gal low-lime mud and also for a 10 lb gal high-lime mud. Typical Properties of a Low and High Lime Mud

Acid Soluble and Clay Free Systems

Ground calcium carbonate is commonly used as a bridging agent in acid-soluble and clay-free systems. It is 98 soluble in 15 HCl, and is available in a wide range of particle sizes from several millimeters down to a few microns and may be used at any temperature encountered in the well. It has been found that, if suitable size ranges are selected, suspensions of calcium carbonate alone can be used for short term remedial work in gun perforated wells. However, for most purposes it is necessary to...

Clay Chemistry Structure of Clays

Clays are minerals which in the presence of water and agitation will adsorb water and break up into colloidal-sized particles. Each particle is only a few microns in thickness and consists of two or more discrete layers. The degree to which the clays dissociate is governed by the clay type, exchangeable cations associated with the clay, and the electrolytic make-up of the water. Clays are hydrous aluminum silicates composed of alternating layers of alumina and silica. Silica is a tetrahedral...

Differentiating Drill Solids from Bentonite by CEC Ratio

At this point, the low-gravity and high-gravity solids have been calculated as volume percents and also as pounds per barrel. Often this is sufficient information for the type of solids control required. But, for high-density muds it may be desirable to mathematically split the low-gravity solids into inert drill solids and active bentonite solids. The reason to know the bentonite in and drill solids separately for high-density muds is to have sufficient bentonite in the mud for good filtration...

Toxic Components in Drilling Fluids

Because formulations for mud additives are continually undergoing change, the Drilling Representative should be aware of certain additives that are considered toxic. EPA priority pollutants include various trade metals zinc, chromium, lead, mercury, cadmium, nickel, asbestos, and various phenol compounds. Chromium is a highly controversial issue the EPA defines toxic chrome as Cr 6 or in a hexavalent state . In drilling fluids, the chrome exists in a trivalent state Cr 3 and the process to...

Types of Formation Damage from Fluids used in Completion

Formation damage, either chemical or physical, reduces the productivity of a well. The basic causes of formation damage are Hydration of formation clays Paraffinic or asphaltic plugging Migration dispersion of formation clays One or more of these causes may exist simultaneously in a well. Selecting a properly designed, compatible fluid is a means of mitigating these effects.

Indirect versus Direct Displacement

Two different displacement procedures are outlined the indirect displacement and the direct displacement. The choice of procedure depends on casing-tubing strengths and cement bond log results. If the bond logs and casing strength data indicate that the casing will withstand a calculated maximum pressure differential, the indirect displacement procedure should be used P BHP - HH due to sea-water . This procedure uses large volumes of seawater or drillwater to flush the well and results in a...

Pilot Testing Equipment

A balance that can weight from 0.1 to 300 g and an oven preferably roller oven that can go to approximately 400 F are needed. Mud cells three minimum made of stainless steel to hold at least 300 cm3 of mud at 1000 psi, a mixer such as a Hamilton Beach mixer are also needed. Mud testing equipment that is accurately calibrated, along with fresh reagents for titrations are essential for pilot testing. Most mud companies can provide a Pilot Test Kit, they do not usually contain the oven and cells,...

How To Decrease Ph In Drilling Fluid

Generally, increased pressure results in the increased solubility of CO2 in water. Increases in temperature normally decrease the solubility of CO2 in water. Dissolved minerals tend to buffer or to prevent the reduction of pH in a water associated with CO2, thereby influencing the rate of corrosion in a given system. Determination of Carbon Dioxide in Drilling Muds Carbon dioxide can be identified in the drill mud by several means Increase in HCO3 and CO3 content Iron carbonate, magnesium...

Lime Muds

Lime muds may be used where an inhibitive mud is desired and where temperatures do not exceed 300-325 F. They are particularly useful because of their high solids tolerance. These muds vary widely in their range of filtrate alkalinities and lime content and are generally grouped into three broad categories as shown in Table 5. Lime Mud Classifications Based on Alkalinity Ranges The pH range for lime muds is from 10.5-12.5. Soluble calcium varies between 120-400 mg L, and is controlled by the...

Foam Drilling

Foams can be classified as Foam, Stiff Foam and Stable Foam for discussion purposes. They are in many ways similar type drilling fluids. Foam is differentiated from mist by the fact that foams may contain a blend of water, polymers, clays, surfactants and corrosion inhibitors. Transition from mist to foam may be necessary when difficulties are encountered while using dry gas or mist. Some of these problems are hole erosion, inadequate hole cleaning, loss of returns and water flows. Foam...

Brittle Shales

Clay Swelling

These shales appear quite firm and competent, but fall to pieces when placed in water. The pieces do not soften or swell in the water. Instability of brittle shales can be caused by either of two mechanisms. The shale can be weakened by hydration of micro-fracture surfaces, and bedding planes, parting within the shale structure. The second mechanism results when a small amount of clay is surrounded by a completely non-swelling quartz and feldspar matrix. Even slight hydration of the clays will...

Ph kMWd

Ph Hydrostatic Pressure MW Mud Density k .052 when d Feet, k .0069 5 when d Feet, k Conversion Constant d Depth TVD MW lb gal, Ph Psi MW lb ft3, Ph Psi MW g cm3, Ph Atmosphere The 0.052 conversion factor is derived in the following manner Water Density, 1130 1 ft2 V 1 gal Conversion I ft3 A Area, in.2Awater Density- It-J Factor 62 30 lb 1 ft2 1 gal _ 0.0519 gal I ft3 A 144 in.2A 8.3 f Note 62.30 lb is the weight of 1 ft3 of water at 60 F and 8.33 lb is the weight of 1 gal of I water at 60 F....

Water Based Drilling Fluids Testing Procedures Mud Density

Mud Density is used to control subsurface pressures and stabilize the wellbore. Mud density is commonly measured with a mud balance capable of 0.1 lb gal accuracy. A mud balance calibrated with fresh water at 70 5 should give a reading of 8.3 lb gal. 4. Measure and record the temperature of the sample of mud to be tested. 5. Place the mud balance base on a flat, level surface. 6. Fill the clean, dry, mud balance cup with the sample of mud to be tested. Rotate cap until it is firmly seated....

Oil Mud Calculations

The following set of calculations describe how to either raise or lower the oil water O W ratio of an oil-based mud. If water enters an oil mud, the O W ratio will decrease and if the O W ratio is to be raised, then oil will have to be added. The amount of oil required to raise the O W ratio can be calculated as follows If the O W ratio is desired to be lowered, then water must be added based on the following equation Lower oil water ratio - add water water x How much oil is required to...

Troubleshooting and Contamination

Lignite Lignosulfonate Deflocculated Muds. Lignite Lignosulfonate Deflocculated Muds are fairly resistant to contamination. Table 4 shows typical contaminants, indicators of contamination, and treating strategies as well as recommended troubleshooting practices for product quality. Contaminant Treating of Lignite Lignosulfonate Muds Increasing PV, retort solids, gels. Thick mud on bottoms-up after trips. Major dilution. Improve solids removal. Centrifuge mud. Increasing PM, PF, pH, YP gels, and...

Concentration and Size Distribution of Solids

Concentration of solids in a mud is usually measured as volume percent by an API retort test. Concentration as measured by the retort cannot indicate the total surface area of the solids, which is the main cause of mud problems. Another API test, the methylene blue test, gives an indication of total surface area of active solids. These tests, taken together, can help define when solids will cause a mud problem. For example, a high MBT value indicates a large surface area of solids in a mud even...

Pseudoplastic Fluids

These fluids are characterized by the shape of the flow cure illustrated in Figure 6. When the shear stress shear rate plot of such fluids is made on logarithmic scale, a straight line is obtained. The effective viscosity of a pseudoplastic fluid decreases with increasing shear rates. For drilling fluids, pseudoplastic behavior is usually defined by using the Power Law equation. The Power Law equation uses two parameters, K and n. K is a measure of a mud's consistency at very low shear rates....

Oil Mud Applications

Oil muds offer many advantages over water based muds. The high initial cost of the oil based mud can be a factor in not selecting this type of mud system. However, if the overall drilling costs are considered, the costs accompanying the use of an oil mud are usually less than that for a water mud. Some of the applications of oil-based muds will be described below. Shale Stability - Oil muds are most suited for drilling water sensitive shales. Formulated with the proper salinity, oil muds can...

Principal Additives of Gyp Muds

Principal additives of gyp muds are similar to the lime muds. Exceptions are that concentrations of deflocculants and fluid loss additives are higher. Table 16 lists the principal additives used in formulating and maintaining gyp muds. Table 16 Principal Additives for Gyp Mud Bentonite - Prehydrated bentonite is added to increase viscosity and control filtration. Gyp - Gypsum provides Ca ion for base exchange of clays from Na to Ca for inhibition. Calcium ion level is maintained from 200-1200...

Oil Based Muds

Under most conditions, conventional oil-based muds are excellent for drilling through a production interval. Low mud spurt loss minimizes particle invasion and the filtrate, being oil, does not cause water-block or damage water-sensitive formations. Both laboratory and field tests have shown that oil muds are less damaging to water-sensitive formations than conventional water-based muds. Oil muds can cause wettability changes, however, and are unsuitable for use in dry gas reservoirs. Oil muds...

Interpretation of Pilot Test Results

Weighing Eqipment Drawing

A single pilot test can give only limited information, but this is often sufficient for the need. Most often a series of pilot tests three to five samples are required to properly answer the questions. For every Specific Gravity of Common Drilling Fluid Components Specific Gravity of Common Drilling Fluid Components pilot test single or series a control sample must be run along in parallel with the test sample. A control sample is the base mud which has not been treated, but which is taken...

Free Oil Sheen

As mentioned previously, definitions are critical in interpreting environmental regulations. The sheen test, for example, is especially pertinent. Note that there are three tests for sheen, each with a slightly different meaning, but with a significant impact on compliance. The Alaska sheen evaluation criteria is based on a bucket test however, the sheen definition criteria states that the sheen must cover greater than one half of the surface area of the container. On the other hand, the Gulf...

Water Based Drilling Muds

As a general rule, water-based drilling muds are not suggested for use as packer fluids. Exceptions to the rule are the use of low-density drilling fluids in shallow areas of relatively low temperature. Water-based drilling fluids are susceptible to extremes of temperature and can solidify with long-term exposure to downhole conditions. Lime-based drilling fluids are particularly susceptible to high temperature gelation. Settling and corrosion, whether from electrolytic or bacterial action are...

Salt Based Muds

To eliminate confusing terminology, any references to the term salt in this manual will herein refer to sodium chloride, unless otherwise stated. Therefore, salt-based muds are muds containing varying amounts of predominantly sodium chloride ranging from 10,000 mg L NaCl up to saturation, 315,000 mg L NaCl. However, when referring to chloride ion concentration which is colorimetrically titrated and reported on the Drilling Mud Report, chlorides will mean chlorides from any source such as...

Filtrate Alkalinity Resulting from Caustic Soda Addition

Note For a 1-cm3 increase in PF above 7.0 cm3, it will require approximately one additional pound per barrel of caustic soda. Approximately 20 additional lime should be added during conversion to obtain the desired amount of excess lime after the conversion is completed. For example, if 8.0 lb bbl excess lime are required, approximately 10.0 lb bbl lime should be added at the time of conversion. Also, if barite is added to the mud to increase density, it will take approximately two to three...

Lithium

Lithium ion, as lithium chloride, is also used as a tracer. The use of lithium provides several advantages over the other tracer techniques. Lithium does not undergo a base exchange on the clays it is temperature-stable and non-biodegradable. Lithium does not affect the drilling fluid properties and can be accurately determined in low concentrations. The major drawback to the use of lithium is the detection process used to determine lithium concentrations. The quantitative determination of the...

Shale Stabilization with Drilling Fluids Oil Based Muds

The hydratable, dispersible, and brittle shales are all sensitive to water. Instability can be partially eliminated by preventing the water in the drilling fluid from contacting the shale. One solution is to use an oil-based fluid where water is emulsified in the continuous oil phase. The interfacial film surrounding the emulsified water droplets in an oil mud can act as a semipermeable membrane and provide a mechanism for osmosis. Osmosis is the flow of water from a less concentrated salt...

Principal Additives of Brackish Water Muds

Although additives and concentrations are essentially the same as for Saltwater Muds, Brackish-Water Muds generally are not as difficult to maintain because of their lower makeup water salinity. However, because of the nature of brackish water environments, both organics and bacteria may cause increased consumption of additives. Principal Additives of Brackish-Water Muds Bentonite - bentonite is added for viscosity and filtration control in brackish-water muds. The bento-nite should be...

Principal Additives for High Temperature Therma Dril

Principal Additives of THERMA-DRIL Muds Corrosion Control Temperature Stability y THERMA-THIN - THERMA-THIN is a liquid polyacrylate terpolymer used to reduce the viscosity of the mud and functions extremely well in reducing high-temperature gelation. THERMA THIN is also effective in the presence of chlorides and aids in filtration control. It is used to pretreat the mud system prior to drilling cement. This product does not contain any chrome. THERMA-CHECK - THERMA-CHECK is a vinylsulfonate...

Gyp Muds

Originally, gyp muds were used for drilling massive sections of anhydrite. Lack of an effective deflocculant confined their use to low-density muds that normally possessed high viscosity and high gel strengths, until the introduction of chrome lignosulfonate as a deflocculant. Gyp mud systems are less susceptible to high-temperature solidification than lime muds due to their lower alkalinity values. If the PF is kept low 0.1 to 0.4 , a gyp mud may tolerate temperatures up to 350 F however, they...

Introduction

This is a summary of solids control concepts dealing with the basics of solids removal techniques and the capabilities of various mechanical devices. For more comprehensive detailed information on these devices, refer to Amoco's Solids Control Handbook. The purpose for implementing a solids control program is to improve the performance of the mud's basic functions, which are 1 to build a low-permeability, thin, slick filter cake on the borehole wall, 2 to provide efficient drilling hydraulics,...

Solids Contamination

Among the various contaminants discussed in this section, excess solids are by far the most prevalent and detrimental to all types of drilling fluids. Solids problems are often magnified by the presence of other contaminants because excess solids and contaminant ions can strongly interact to create a more serious mud problem than either one separately. Sources of solids in a mud are threefold 1 cuttings or sloughings from the wellbore, 2 commercial solids added to the mud, and 3 chemically...

System Makeup

KCl-Polymer Muds should be built from scratch as follows 1. Treat makeup water with 0.25 lb bbl soda ash and 0.12 lb bbl caustic potash to remove calcium and magnesium. However, if the makeup water does not contain magnesium, the caustic potash may be omitted. 2. Prehydrate bentonite in fresh water. 3. To mix polymers, start with the viscosifying polymers first. If the mud becomes too thick to efficiently pump, add potassium chloride. The salt will reduce the viscosity. Adjust pH range to...

Chromate Inhibitors

When the scavengers cannot be used effectively, there are several inhibitors available for use in drilling fluids. Zinc chromate and sodium dichromate are inhibitors which coat the drill pipe to protect against the corrosive environment. Use of chromates is prohibited in some areas due to environmental regulation. The chromates are in liquid form and come in 55-gal 0.21 m3 drums. Injection of the material is done in a manner similar to the scavengers. When using the chromates, it is recommended...

Functions of Drilling Fluids

Results of extensive research at both Amoco Production Research, Tulsa, and in the field show that penetration rate and its response to weight on bit and rotary speed is highly dependent on the hydraulic horsepower reaching the formation at the bit. Since the drilling fluid flow rate sets the system pressure losses, and these pressure losses set the hydraulic horsepower across the bit, it can be concluded that the drilling fluid is as important in determining drilling costs as all other...

Principal Additives for High Temperature Deflocculated Pyrodril Muds

Principal Additives of PYRO-DRIL Mud Systems PYRO-VIS - PYRO-VIS is a sugar beet extract which acts as a supplemental viscosifier to increase carrying capacity without the addition of bentonite. This product requires a shearing device to fully develop viscosity. PYRO-VIS is not affected by chlorides or other contaminants such as carbon dioxide and calcium from anhydrite. MILTEMP - MILTEMP is sulfonated styrene maleic anhydride. This product is a powdered deflocculant used to reduce viscosity...

The Drilling Mud Report

Drilling Mud

The following example problems introduce some of the basic engineering calculations related to the Drilling Mud Report. The drilling mud report is a good commuications tool and when filled out completely and accurately, can be used to anticipate potential problems and assist in future well planning. Figure 1 Wellbore Configuration for The Drilling Mud Report Example Problem Figure 1 Wellbore Configuration for The Drilling Mud Report Example Problem Pump Make til t OAMf Assumed Model O-P-t30 Eff

Mechanically Induced Shale Instability

Mechanical instability is generally the end result of excessive, erratic contact of the drill string with the wellbore wall, and or excessive pressure losses and surges generated by the flowing fluid in the annu-lus. Proper bottomhole assembly selection and sound fundamental drilling practices will do all that can be done to minimize the first of these causes. Annular pressure loss control involves constantly monitoring annular rheology and hydraulics. As a guide, if the calculated annular...

Lignite Lignosulfonate Deflocculated Muds

Lignite-Lignosulfonate Muds can be used to drill a variety of formations. They can be weighted up to 18 or 19 lb gal, provided low-gravity solids bentonite and drill solids are in the proper range. As mud density is increased, the bentonite content should be decreased. The pH range for controlling lignite-lignosulfonate muds is in the 9.5 to 10.5 range. In this range, the magnesium ion is precipitated. Calcium ion should be kept below 200 mg L. Less than 10,000 mg L chlorides should not hamper...

Nomenclature

Specific Gravity Weight Material SGWM 1. Volume Increase - The general mud weight increase formula is used for any weight material where SGWM is the specific gravity of the weight material and MW and MWF are the initial and final mud densities in pounds per gallon. . . total pounds weight material 2. No Volume Increase - To determine the initial volume of mud, VI, to start with to attain a final volume VF, the starting volume is defined by To calculate the pounds per barrel of weight material...

Stiff Foam

Stiff Foam is another type of foam classification. It is rheologically more like a mud than ordinary form. It is a low-density drilling fluid used to drill poorly-consolidated formations in which hole-stabilizing materials can be included. The stronger foam supports larger cuttings compared to simple foam. When stiff foam is used, the annular velocity can be from 100 to 200 ft minute for adequate hole cleaning. Consequently, compressor requirements are much less than for other types of...

Trouble Shooting Oil Muds

Add water and emulsifier, add gellant. If high temperature add polymeric viscosifier. All of these affect the low-shear viscosity, gel strength and yield point more than the plastic viscosity. Remove low gravity solids with solids control equipment and or dilution. Increase o w ratio if water content is too high. Add oil wetting agent to reduce viscosity. Remove water wet solids and add oil wetting agent and oil. Ensure that there is no insoluble calcium chloride in the mud. Water wet solids...

Specific Gravity

The density of any material is derived by multiplying the specific gravity of that material by the density of pure water. For example, the specific gravity of barite is 4.2 and its density is equal to 4.2 8.33 lb gal 35 lb gal. Conversely, to convert from density to specific gravity, divide the density of a material or mud by the density of pure water. As an example, a 17.5 lb gal mud has a specific gravity of 2.1. To determine the weight of 1 bbl of barite, determine the density of 1 bbl of...

Advantages Disadvantages of Non Dispersed Polymer Muds

Advantages Disadvantages of Polymer Muds Irreversible adsorption of the polymer on clays Easily converted to a deflocculated system Requires more dilution than deflocculated systems More corrosive than deflocculated systems Sensitive to contaminants carbonate contamination difficult to treat Contamination - Non-Dispersed Polymer Muds Contaminant Treating of Non-Dispersed Polymer Muds Increasing retort solids, PV, YP, gels, MBT. Thick mud on bot-toms-up after trips. High flowline viscosity....

Annular Velocity

What is the annular velocity at 110 SPM on one pump, opposite a. Drill Collars Open Hole AV0h dc _ft min b. Drill Pipe Open Hole AV0H DP _ft min c. Drill Pipe Casing AVCSG DP _ft min The annular velocity defines the average velocity at which the mud passes through a specific annular space and is normally expressed in units of ft min. The following annular velocities opposite specific intervals will be based on pump output at 110 SPM and 94 volumetric efficiency. a. Drill Collars Open Hole, AV0h...

Pump Output

What is the pump output Q in barrels per stroke bbl STK and gallons per stroke gal STK at 94 volumetric efficiency A National 10-P-130 which has a 10-in. stroke with a 5-1 2 in. liner at 100 volumetric efficiency will deliver 3.0996 gal STK. Triplex Single Acting Mud Pump Capacities Per Cycle Barrels per Stroke -100 Volumetric Efficiency Duplex Double-Acting Mud Pump Capacities Per Cycle Barrels per Revolution - 90 Volume Efficiency - Rods Deducted Therefore, at 94 volumetric efficiency a....

Pills and Spacers

Both direct and indirect displacement procedures utilize pills and spacers for effective hole cleaning and separation of fluids. The primary purpose of a spacer is to provide complete separation of two incompatible fluids. The spacer must be compatible with both the displaced fluid and the displacing fluid. Cleaning pills are used to scour and sweep debris out of the hole. Two types of pills may be used. A basic cleaning pill is composed of viscosified drill water, seawater or brine. A scouring...

Lignins and Tannins

These include sulfonated tannins, quebracho, lignosulfonates, lignites and lignite derivatives. The mechanisms by which they work is by thinning the clays adsorbing on the positive edges of the clay platelets, which leads to repulsion among the platelets , plus plugging action of the particles themselves. These additives improve the distribution of solids within the drilling fluid by deflocculating solids such as bentonite and through the colloidal nature of the chemical, skewing the particle...

Viscosifying Agents

The material used to maintain viscosity in the packer fluid will vary with the type of fluid used. Bento-nite, of course, is a viable and inexpensive choice for use in fresh water fluids. Several polymers are available for use in the clear brines as well as in fresh water. CMC and polyacrylonitriles may be used, but polymers such as xanthan gum, HEC and other starch derivatives are frequently chosen, because they are partially or completely acid soluble. This acid solubility enables the...

Static Filtration

When drilling fluid is not circulating in the wellbore and there is no pipe movement, static filtration takes place. With static filtration, the filter cake continues to increase in thickness while the rate of filtration decreases. Filter presses measure static filtration, giving filtrate loss and cake thickness data under time and pressure 30 minutes, 100 psi . This is not an accurate representation of downhole filtration and more complex instruments are needed to duplicate downhole...

Settling Plug Mixing Procedure

Clean and flush all mixing lines to and from cement mixing equipment. Arrange for weight material to be mixed rather than cement. This may require the use of sacked weight material. If sacked weight material is to be used, be sure that weight material sufficient for the plug can be placed near the mixing hopper. Estimate manpower and barite moving requirements forklift and or crane . 2. Measure mixing water for plug volume take into account line volumes into tank. If possible, mix caustic...

Principal Additives of Low Solids PHPA Muds

Principal Additives of Low-Solids PHPA Mud Solids Encapsulation Borehole Stability, Viscosity Bentonite - Bentonite is added for viscosity and filtration control. Since PHPA polymer effectively encapsulates bentonite particles and limits hydration. It is recommended to prehydrate bentonite before adding PHPA. Caustic Soda Caustic Potash - NaOH or KOH is added sparingly for pH and corrosion protection. The pH of the mud should not exceed 9.5 unless conditions dictate otherwise. At this pH all...

Principal Additives of Low Solids Paccmc Muds

Table 47 lists principal additives for formulating Low Solids PAC CMC Muds. These muds just as Ben-Ex Muds, contain few additives and are relatively easy to maintain. Low Solids PAC CMC Muds are also relatively inexpensive compared to other LSND polymer fluids. Table 47 lists principal additives for formulating Low Solids PAC CMC Muds. These muds just as Ben-Ex Muds, contain few additives and are relatively easy to maintain. Low Solids PAC CMC Muds are also relatively inexpensive compared to...