Example Problem

Calculate how many sacks of barite are required to increase the density of an 800 barrel mud system from 12.7 lb gal to 14.5 lb gal. W2 34.9 lb gal (density of barite) therefore 800(12.7) + V2(34.9) (800 + V2) x 14.5 10,160 + 34.9V2 11,600 + 14.5V2 20.4V2 1440 70.6 bbls x 14.7 sk bbl 1038 sacks of barite

Lbs sqft

YP 300 rpm reading - PV or YP (2 x 300 rpm reading) - 600 rpm reading This gives a Bingham yield point, which is generally higher than the actual or true yield. As stated earlier, at low shear rates, the Bingham model does not give particularly good readings. High viscosity, resulting from a high yield point is caused by 1. Introduction of soluble contaminants such as salt, cement, anhydrite, or gypsum, which neutralize negative charges of the clay particles, resulting in flocculation. 2. The...

Self Check Exercises

What should be the response of INTEQ personnel if borehole problems point towards inadequate hole cleaning 2. How can Shale Factor (CEC) be of assistance in predicting hole problems 3. What is the most common indication of hole problems when the rig is performing reaming operations 4. When using the Stuck Pipe Equation, how is DP determined 5. What piece of mud test equipment is used to measure the friction coefficient

Gauge Protection

Protection of the gauge surface is vital to the effectiveness of any bit. The gauge surfaces constantly ream the hole, and thus are subject to continuous abrasive wear. Applying tungsten carbide in a steel matrix through a welding process, called hardfacing, provides the best resistance to this type of wear. Gauge protection is improved as the amount of hardfaced surface area increases. The configuration of the gauge teeth determines the available surface area. The A type teeth are standard for...

The Time Factor

The total amount of time taken to implement and complete kill procedures is important, especially if the kick is gas. This is because the gas bubble will percolate up the annulus, increasing annular pressures. There may also be a danger of the pipe sticking, especially if a fresh water mud system is in use. Invading saline pore water may cause the mud cake to flocculate, so the bit, stabilizers and collars would be in danger of sticking. Considerable time is involved in weighting up the mud,...

Component of weight acting along borehole W BF cos

where 0 is the borehole inclination Extending this discussion to the whole BHA, Wbit Wbha (BF) cose where Wbha is the total air weight of the BHA and Wbit is the weight on bit. Therefore, if no drill pipe is to be run in compression percentage safety margin where the safety factor 1 + -- (DC) - For example, to allow a 10 safety margin the safety factor in the formula would be 1.1 N W(BF) sin e Force W (BF) cos e * Buoyed Weight W(BF) A. Drilling 17.5-inch hole with a roller cone bit, we want...

Drilling Fluid Properties

For those working at wellsites, a basic knowledge of fluid properties is required, especially those properties that distinguish fluids from solids. Fluids can be either a gas or a liquid, where gases are highly compressible and its volume being dependent upon pressure and temperature. Liquids, on the other hand, are only slightly compressible, and their volume being only slightly dependent upon temperature. We shall be dealing with only liquids in this text. Since drilling muds are commonly...

Fractured Faulted Formations

These are naturally occurring formations. When the fractured or faulted formation is drilled, there will be a tendency for pieces of the formation to fall into the borehole. The size of the pieces will vary from pebbles to boulders. They will more commonly occur in limestones and shales. Preventive measures include 1. Clean out excess fill before drilling 3. Place the jar in the heavy-weight pipe section 4. Be prepared to wash ream when tripping in 5. Design a BHA to minimize the risk of...

Advantages of Jetting

It is a simple and cheap method of deflecting well bores in soft formations. No special equipment is needed. Dogleg severity can be partly controlled from surface by varying the number of feet jetted each time. The survey tool is not far behind the bit, so survey depths are not much less than the corresponding bit depths. Orientation of tool face is fairly easy. The same assembly can be used for normal rotary drilling.

Maximum Adjustment of AKO Motors

On the adjustable sub kick off housing, the angle is infinitely adjustable from 0 up to the maximum 3-3 4 tool size is 2.2 4-3 4 tool size is 2.5 6-3 4 tool size is 2.75 9-1 2 tool size is 2 11-1 4 tool size is 2 The addition of an alignment bent sub, with a 2 tilt angle, above the motor section allows the tool to achieve build rates up to 24 100 ft. This is the Double Adjustable Motor (DAM). Major components include Standard NaviDrill bearing and drive sub assembly with short gauge, straight...

Annular preventer

Commonly referred to as a bag type or spherical preventer, it is designed to stop flow from the well using a steel-ribbed packing element that contracts around the drill pipe. The packer will conform to the shape of the pipe that is in the bore hole. It is operated hydraulically, utilizing a piston acting on the packer. Once closed they utilize the upward well pressure to maintain their closed position. These preventers are available for a variety of working pressures, ranging from 2,000 to...

Jet Circulation Bits

Jet circulation bits (Figure 3-3b), are manufactured with smooth, streamlined, fluid passageways in the dome of the bit. Drilling fluid passes through the bore of the bit at high velocities with minimum pressure losses, through the jet nozzles, and then to the hole bottom to flush cuttings away from the bit and up the hole. Excess fluid that impinges on the hole bottom Figure 3-3a Regular Circulation Figure 3-3b Jet Nozzle Circulation Air or Gas Circulation Bits Figure 3-3a Regular Circulation...

Running casing

A kick that occurs while running casing can lead to extreme problems. Stripping the casing to bottom should only be attempted if the guide shoe is within a few joints of bottom. If only a short section of casing is in the hole, the annular pressure will tend to force it upwards, in which case the casing will need to be tied down and filled with drilling fluid immediately. With a long section of casing, it becomes more likely that the combination of tensional forces, the annulus pressure, and...

Baker Hughes INTEQ

The path of the drilled well is plotted on the horizontal projection by plotting total North South coordinates (Northings) versus total East West coordinates (Eastings). These coordinates are calculated from surveys. Field Field 5 - JRG Location North Sea Field Field 5 - JRG Location North Sea Figure 5-18 This is a 3-dimensional turn on the horizontal plan. Lead angle Figure 5-18 This is a 3-dimensional turn on the horizontal plan. Lead angle In the old days (pre 1985) it was normal practice to...

PDMs vs Turbines with a Bent

For directional work with a bent sub, PDMs offer several advantages over turbines. When drilling with a PDM, the directional driller can use pump pressure as a weight indicator. If the pump pressure is constant, the differential pressure across the PDM is constant, so torque and WOB are constant. It is also much easier to tell if a PDM has stalled because there will be an immediate increase in surface pressure. PDMs give a longer bit life than turbines because of the slower rotary speed. They...

Other Components

In addition to the annular and ram type components, the BOP stack must contain some mud access line, and a drilling spool will be inserted into the stack to allow for the connection of these choke and kill lines. The BOP stack will be attached to the casing string via a casing head. This casing BOP connection will have a pressure rating similar to the rest of the BOP components. In certain cases, it may be necessary to allow the well to blowout in a controlled manner rather than be shut-in....

Torque Drag

Several factors affect hole drag, including hole inclination, dogleg severity, hole condition, mud properties, hole size, and drillstring component types, sizes and placement. However, as mentioned earlier, in drilling situations where the drillstring is not rotated (as when a steerable system is used in the oriented mode) axial drag can become very significant and should be evaluated using a Torque and Drag computer program. Torque and Drag programs can be found in EC*Track and DrillByte.

Plugged or Packed Off

If one or more bit jets become plugged, the SIDP will increase suddenly while a constant pump rate is maintained. The choke should not be opened to maintain a constant drillpipe pressure, as this will allow the influx of more fluid. The pump should be stopped and the well shut in. The SPR should be redetermined and this new pressure maintained as the pumps are brought up to the new slow circulating rate, without encountering excessive drill pipe pressures. These new pressures should be used to...

Drilling Trend Workbook

Effectiveness of jetting involves turning the rotary table a few degrees (15 ) right and left while jetting. Having jetted 3 to 8 feet of hole (the exact distance depending on required build rate and previous results) drilling is started. The circulation rate is now reduced to about 50 . Hole cleaning considerations are ignored while drilling the next 10 feet or so. High weight on bit (40 - 45 Klb) and low rotary speed (60 70 RPM) should be used to bend the assembly and force it to follow...

Hif x Hps Fixed Cutter Bit Hydraulics

The hydraulics for fixed cutter bits is based on the drilling fluids ability to remove cuttings beneath the cutters and to cool the bit. Fluid volume is critical to PDC bit performance. Fluid volume and fluid velocity is critical to diamond bit performance. The major components of fixed cutter bit hydraulics are 1. flow rate - Q (gal min) and V (ft min) 2. drilling fluid characteristics - MD (lb gal), YP (lbs 100ft2) and PV (cps) 3. pressure loss - across the bit face (diamond bit) or through...

Table

Principle compounds in portland cement Tricalcium Silicate - 3CaO SiO2 - C3S 1. The major compound in Portland cement 2. Contributes to strength development, especially during the first 28 days 2(3CaO SiO2) + 6H2O ---> 3CaO 2SiO2 3H2O + 3Ca(OH)2 Dicalcium Silicate - 2CaO SiO2 - C2S 1. A much slower hydrating compound than tricalcium silicate 2. Contributes to a slower, gradual increase in strength, over an extended period of time 2(2CaO SiO2) + 4H2O ---> 3CaO 2SiO2 3H2O + Ca(OH)2 Tricalcium...

Running Drill Pipe In Compression Example

Prior to drilling a 12.25-inch tangent section in a hard formation using an insert bit, the directional driller estimates that they expect to use 50,000 lbs WOB. The hole inclination is 60 and the mud density is 11 ppg. What air weight of BHA is required if we are to avoid running any drill pipe in compression Use a 15 safety margin. This is roughly the weight of ten stands of 8-inch drill collars, or attentively, six stands of 8-inch collars plus 44 joints of HWDP This is just not practical It...

Mobile Formations

These are naturally occurring plastic formations. Most commonly shales and salt. When drilled, they will tend to flow into the borehole. Preventive measures include 1. Recognize there is a reaction time associated with these formations 2. Regular wiper trips are normally required 3. Condition the mud prior to drilling those formations 4. Use eccentric PDC bits to drill these formations 5. Increase the mud density if possible If the drillstring becomes stuck in a mobile formation, the annulus...

Hydraulics

The concept that a fluid cannot maintain a rigid shape is a basic, but important characteristic, which means that fluids cannot sustain a shear-stress (a tangential force applied to the surface). Any tangential force will cause the fluid to deform and continuous deformation is known as flow. Fluid flow is always considered to take place within a conductor. A conductor may be the annulus created by casing for drilling fluid or a volcano's slope and the atmosphere, in the case of a lava flow....

Funnel Viscositysecqt

The Marsh Funnel is the field instrument used to measure viscosity. It is graduated so that one quart (946 cc) of water will flow through the funnel in 26 seconds. To run a test, the bottom orifice is covered and drilling fluid is poured over a screen until the funnel is full. When the bottom is uncovered, the time required to fill one quart is recorded (in seconds) along with the temperature. Funnel viscosity is a rapid, simple test, but because it is a one point measurement it does not...

Sand Content vol

This is measured by use of a 200 mesh sand screen set. A measuring tube is filled with mud and water and shaken vigorously. The mixture is then poured over the 200 mesh sieve and washed clean with water. The sand is then washed into the measuring tube and measured in percent. This will give an indication as to the effectiveness of the mechanical solids control equipment. A retort is used to determine the quantity of liquids and solids in a drilling fluid. A measured sample of fluid is heated...

Effects of Drill Collar OD

When using a fulcrum (build) assembly, reducing the collar OD will dramatically increase the build tendency, because the collars will be more limber and will bend more. Another factor is the clearance between the outside of the drill collars and the wall of the hole. The greater the clearance, the more the collars can bend before they contact the low side of the hole. Once the collars contact the low side of the hole, further increases in WOB will have only a marginal effect on build rate by...

Upon completion of this section you will be able to

Explain how drill pipe grades define the yield strength and tensile strength of steel. Explain how drill pipe is classified. Calculate total yield strength for a specific grade class of drill pipe. Explain the effects of buoyancy on the drillstring. Calculate the buoyed weight (or hookload) in a vertical hole. Explain the causes of varying hookload during the drilling process. Explain overpull and calculate the maximum permitted pull. Calculate required BHA air weight for applications where...

Bha Configuration For Reaming Directional Holes

During trips out of the hole, the common indication of stuck pipe problems will be increased drag and overpull. 1. Are problem formations exposed above the bit 1. Review records of previous trips. Is there a trend which can be related to a possible cause 2. Are high swab pressures resulting in hole 2. Check if the proper lag time was completed when circulating bottoms up 3. Was the hole adequately cleaned prior to the trip 3. Check swab pressures, should the trip speed be reduced. 4. Were...

Air Mist Foam Based Mud Systems

These lower than hydrostatic pressure systems are of four types 1) dry air or gas is injected into the borehole to remove cuttings and can be used until appreciable amounts of water are encountered, 2) mist drilling is then used, which involves injecting a foaming agent into the air stream, 3) foam drilling is used when large amounts of water is encountered, which uses chemical detergents and polymers to form the foam, and 4) aerated fluids is a mud system injected with air to reduce the...

Example

For a horizontal well proposal, the maximum tensile loads have been calculated using a Torque and Drag program assuming that 5-inch drill pipe will be used. In the 8.5-inch hole section, the anticipated loads at the end of the build and at TD of the horizontal section are Using 90 of the yield strengths quoted in RP7G and including a margin of 100,000 lbs overpull, the maximum tensile loads which can be applied to 5-inch, 19.5 lbs ft, API class 2 drill pipe (worst case) are In this worst case...

Parts of Speech

Names of the words used in a sentence. There are eight parts of speech-noun, pronoun, verb, adjective, adverb, preposition, conjunction, and interjection. The interjection is probably the least used in technical writing. Passive Voice Verb form which indicates the subject is being acted upon. The report was written by the logger. (The same thought expressed in active voice would be Person Relation between the verb and subject showing whether a person is speaking (first person), spoken to...

Low Choke Pressure Procedure

Circulate using the maximum pump rate. 2. Start weighting up the mud to the estimated kill mud density. 3. Begin circulating, while holding the maximum allowable casing pressure by adjusting the choke. Care must be taken, and observe for lost circulation. 4. Circulate out the kick fluid until it reduces the choke opening in order to maintain the maximum allowable casing pressure. 5. Shut-in the well and record the shut-in drill pipe and shut-in casing pressures. The wait and weight (engineers)...

Additional Review Reading Material

Rabia, Hussain, Oilwell Drilling Engineering Principles and Practice, Graham & Trotman, 1985 SPE, Applied Drilling Engineering, SPE Textbook Series, Vol 2, 1986 Moore, Preston, Drilling Practices Manual, 2nd Edition, Pennwell Publishing Company, 1986 Hughes Tool Co. Hughes Tool Co. Hughes Tool Co. Hughes Tool Co. Video Tape, Tri-Cone Bit Design Video Tape, Bit Action On Bottom Video Tape, Dull Bit Grading Video Tape, Introduction To PDC Bits

BHA Weight For Steerable Motor Assemblies

In practice, BHA weight for steerable assemblies on typical directional wells is not a problem for the following reasons. The WOB is usually fairly low, especially when a PDC bit is used. When the drillstring is not rotated, the drill pipe is not subjected to the cyclical stresses which occur during rotary drilling. Therefore, sinusoidal buckling can be tolerated when there is no rotation of the drillstring. Helical buckling however, must be avoided. Helical buckling occurs at 1.41 Fcr, where...

Cost PerFoot Analysis

The introduction of advanced drill bit designs has not always had the effect of obsoleting existing designs. Instead, the availability of new designs has increased the number of types of bits available from the various bit manufacturers. Selection of the bit best suited for a specific use is further complicated by the variable performances and prices of the many types of bits. Thus, the question which needs to be answered is How can the correct bit be selected for a given application The...

Casing Couplings

Couplings are short pieces of casing used to connect the individual joints. They are normally made of the same grade of steel as the casing. Through their strength can be different than the casing. The API has specifications for four types of couplings. Short round threads and couplings (CSG) Long round threads and couplings (LCSG) Buttress threads and couplings (BCSG) The CSG and LCSG have the same basic thread design. The threads have a rounded shape, with eight threads per inch. These...

Adverbial Clause

Subordinate clause used as an adverb answers a question of how, why, when, where, how much. The rig will be built as the engineers specified. (How) A fire started after the motor failed. (When) Word or group of words to which a pronoun refers. The motor that failed was new. (Motor is antecedent of the relative pronoun that) Either definite (the) or indefinite (a, an) used as adjectives. Verb used to form other verbs will, shall, can, may, have, be, do, must, and ought are typical auxiliaries....

Allocation of slots to targets

Even this is not always a simple task. From a directional driller's viewpoint, slots on the North East side of the platform or pad should be used for wells whose targets are in a North Easterly direction. Unfortunately there are other considerations (e.g. water injection wells may have to be grouped together for manifolding requirements). Also, as more wells are drilled and the reservoir model is upgraded, targets can be changed or modified. Inner slots are used to drill to the innermost...

Drill Pipe Yield Strength and Tensile Strength

If drill pipe is stretched, it will initially go through a region of elastic deformation. In this region, if the stretching force is removed, the drill pipe will return to its original dimensions. The upper limit of this elastic deformation is called the Yield Strength, which can be measured in psi. Beyond this, there exists a region of plastic deformation. In this region, the drill pipe becomes permanently elongated, even when the stretching force is removed. The upper limit of plastic...

Navi Drill Mach AD

The Navi-Drill Mach 1 AD motor is designed specifically for use in holes drilled with air and mist. With an AKO, the steerable motor drilling system combines directional and straight hole drilling capabilities to provide precise directional control. Generally, in one run it can establish the desired direction and inclination for the surface interval of a directional well. The AKO places the bend close to the bit, and can be adjusted so the motor housing tilt angle can be configured on the rig...

UTM System

One example of a grid system is the Universal Transverse Mercator (UTM) System. In transverse mercator projection, the surface of the spheroid chosen to represent the Earth is wrapped in a cylinder which touches the spheroid along a chosen meridian. (A meridian is a circle running around the Earth passing through both North and South geographic poles.) These meridians of longitude converge towards the North Pole and do not produce a rectangular grid system. The grid lines on a map form the...

Bottom Hole Horsepower

Determination of the amount of Bottom Hole Cleaning necessary to maximize the drill rate is based upon 1. Hydraulic (Jet) Impact Force Maximizing Hpb involves minimizing Hpc, or in other words, the lowest flow rate and the highest pump pressure will result in the highest Hpb. However, the lowest flow rate will usually result in inadequate bottom hole cleaning. To compensate for this, bottom hole pressure can be increased by using smaller jet nozzles.

Hookload Air Weight x Buoyancy Factor

Buoyancy Factors rounded off to three places can also be found in the API RP 7G (Table 2.13). Note The formula above for hookload does not take into account axial drag. Hookload, as determined in the formula above is the approximate static surface hookload that would be displayed by the weight indicator in a vertical hole with no drag, excluding the weight of the traveling block, drill line etc. In practice, hookload will vary due to motion and hole drag. Pick-Up Load refers to the hookload...

Shutin Procedures

As mentioned earlier, as soon as indications of a kick are noticed, steps should be taken to shut-in the well. If tripping, under no circumstances should the pipe be run back to bottom with the annular preventer open and the well flowing. The primary concern is to kill the well, any concerns about stuck pipe or other well problems should be secondary. Two types of shut-in are possible Hard Shut-In The annular preventer is closed immediately when the pumps are shut off. Soft Shut-In The choke is...

Causes of Kicks

There are 5 major reasons why kicks occur Failure To Keep The Hole Full The majority of kicks occur when the bit is off bottom, while tripping. When the pumps are shut down prior to tripping, there is a pressure reduction in the borehole equal to the annular pressure losses. If the equivalent circulating density and the pore pressure are nearly equal, flow may occur when circulation stops. As pipe is removed, the mud-level in the borehole falls, causing a reduction in hydrostatic pressure. Pipe...

Case Vertical Well Neutral Point in the drill collars

Lnp is the distance from the bit to the neutral point. WDC is the weight per foot of the drill collars BF is the buoyancy factor of the drilling mud. Example Determine the neutral point in 7.25-inch x 2.25-inch collars if the weight-on0bit is 30,000 lbs and mud density is 11 ppg. Lnp is 284 feet up into the collars.

Material Balance Equations

Material balance equations are used for calculating volumes and densities when two or more insoluble materials are mixed together. VjWj + V2W2 VFWF where Vj + V2 VF Volume of first material to be mixed together Density of first material Volume of second material to be mixed together Density of second material Total or sum of all volumes mixed together Density of total mixture. Proportional average of all volumes mixed together The most commonly used variables in material balance equations are...

Forward

The Drilling Engineering Workbook is a correspondence (distributed learning) course which covers the important elements of drilling a well. The emphasis is on the theory behind these drilling elements in order to develop a greater understanding of the principles involved in drilling a well. This is a lesson-by-lesson distributed learning course. Individuals should study each section and then answer the related questions at the end of the section. Supplementary reading is suggested throughout...

Chemical Washes

Chemical washes are fluids containing surfactants and mud thinners, designed to thin and disperse the drilling fluid so that it can be removed from the casing and borehole. Washes are available for water-based and oil-based drilling fluids. They are designed to be used in turbulent flow conditions. Spacers are fluids of controlled viscosity, density and gel strength used to form a buffer between the cement and drilling fluid. They also help in the removal of drilling fluid during cementing. An...

Salt Chlorides

Of distilled water and 5 - 10 drops of potassium chromate solution are added. This mixture is stirred continuously while drops of silver nitrate solution are added until the color changes from yellow to orange red and persists for 30 seconds. The number of milliliters of silver nitrate used to reach the end-point are recorded. This is then used in the equation Chlorides ppm ml of silver nitrate x 1000 ml filtrate This can be converted to salt NaCl ppm by multiplying the chlorides by 1.65, or to...

Hydraulic Impact Force

Hydraulic Jet Impact Force is based on the theory that cuttings are best removed from beneath the bit when the force of the fluid leaving the jet nozzles and striking the bottom of the hole is the greatest. Impact Force is determined by As can be seen, Impact Force depends on maximizing flow rate and nozzle velocity rather than pressure. Therefore, higher flow rates are required. The emphasis is on a large volume of fluid impacting with moderate force, rather than a small volume impacting at a...

Example Break Even Analysis

Trip Time, Hrs 8 Bits 7 hr. each 56 hrs. 53.45 per feet target cost . , Insert Bit Cost T T trip hrs tt-t- t- _ Hours r Rig Cost Hr Plot to left of zero on 'X' horizontal axis Insert Bit Cost Trip Cost Plot footage on 'Y' vertical axis Draw a straight line extending through points A and B 20 40 60 80 100 120 RIG HOURS DRILLING 20 40 60 80 100 120 RIG HOURS DRILLING Any footage and hour combination on this line is a breakeven point above the line is the lower cost ft, below is the higher cost...

ByPass Valve

The by-pass valve allows fluid to fill the drill string while tripping in the hole and to drain while tripping out. When mud is pumped, the valve closes causing fluid to move through the tool. Most valves are of a spring piston type which closes under pressure to seal off ports to the annulus. When there is no downward pressure, the spring forces the piston up so fluid can channel through the ports to the annulus. Figure 5-20 .

Outputs

Information concerning loads, torques and stresses are calculated for discrete points in the drillstring from rotary table to the bit. These values are output in both tabular summary or detailed and graphical formats Rotary torque drilling and off-bottom Maximum allowable hook load at minimum yield Drillstring weight in air Bit to neutral point distance drillstring twist

The Concurrent Method

This is the most complicated and unpredictable method of the three. Its main value lies in the fact that it combines the driller's and engineer's methods, so that kill operation may be initiated immediately upon receipt of the shut-in pressures. Instead of waiting until all the surface mud has been weighted up, pumping begins immediately at the kill rate and the mud is pumped down as the density is increased. The rate at which the mud density is raised is dependent upon the mixing facilities...

Introduction Drilling Engineering Netwas

Oil well cementing is the process of mixing and displacing a slurry down the casing and up the annulus, behind the casing, where is allowed to set, thus bonding the casing to the formation. Some additional functions of cementing include Protecting producing formations Providing support for the casing Protecting the casing from corrosion Sealing off troublesome zones Protecting the borehole in the event of problems The main ingredient in most cements is Portland cement, a mixture of limestone...

Interval drilling

An estimate of the required footage to be drilled in oriented mode can be determined using Footage Oriented DL - DLR DLO - DLR x 100 DL required dogleg 7100' DLO actual dogleg when oriented 7100' DLR actual dogleg when rotary drilling 7100' Example Planned build-up rate 2.57100' Build-up rate obtained when oriented 3.57100' Build-up rate obtained during rotary drilling 0.57100' Footage Oriented 2.5 - 0.5 3.5 - 0.5 x 100 67

Use Of Torque Drag Programs For BHA Weight Evaluation

These programs have a wide range of applications, but have mainly been used to evaluate drillstring design integrity and alternative well plans for horizontal wells or complex, unusual directional wells. However, the program can be used to check BHA weight calculations for normal directional wells. The program will calculate axial drag for a non-rotated assembly and also calculates the position of the neutral point in the drillstring. In addition, the program calculates the forces on the drill...

Drill Pipe Classification

Drill pipe class defines the physical condition of the drill pipe in terms of dimension, surface damage, and corrosion. Drill pipe class is indicated by paint bands on the drill pipe according to the following code Class 1 drill pipe is New and therefore the strongest. As pipe is used, the wall thickness will be gradually reduced. This reduction of the drill pipe cross sectional area results in a lower Total Yield Strength in pounds. This yield strength in pounds can be calculated using the...

Bit Stabilization

A diamond is extremely strong in compression, but relatively weak in shear, and needs constant cooling when on bottom. The bit is designed and the rake of the diamonds set, so that a constant vertical load on the bit keeps an even compressive load on the diamonds, and even distribution of coolant fluid over the bit face. If there is lateral movement or tilting of the bit, an uneven shear load can be put on the diamonds with coolant leakage on the opposite side of the bit. Any of the standard...

Geopressured Formations

These formations have a pore pressure which exceed the hydrostatic pressure of the drilling fluid. If these formations are not permeable for example, shales , once drilled, these formations will cave into the borehole. Preventive measures include 1. Clean the hole of cuttings when not drilling 2. Observe the cuttings for cavings, some being large and convex concave in appearance 3. Increase the mud density if possible 6. Monitor pump pressure for annular loading 8. Minimize the time in the open...

Pressure Loss in the Drillstring

Once passed the surface equipment, the fluid will flow through the drillstring. In hydraulic calculations, these parts of the circulating system are considered circular pipes. In typical field operations, fluid velocities are in the order of 1000 ft min 300 m min . At such velocities, the fluid is in turbulent flow. The pressure required to circulate fluid in turbulent flow varies by approximately 1.8 power of the flowrate. Doubling the flowrate would increase the pressure drop in the...

Preliminary Steps

Before starting test, make sure the bit is properly seated i.e. has the proper bottomhole pattern . 2. Driller and logging personnel should communicate before the start of the test - logging unit to collect data in one second intervals. 3. Lift bit off bottom approximately one foot, stop pumps and rotary speed - wait ten seconds. 4. Start pumps - wait ten seconds 5. Start rotary speed - wait ten seconds 6. Start drill-off test Example Drill-Off Test Parameters 1. Maintain each WOB for 60...

Reactive Formations

These are naturally occurring bentonitic shales, generally known as gumbo shales. The clays within the shales react with the mud filtrate and hydrate. The hydrated shales will then fall or swell into the borehole. When drilling, the bit tends to ball-up with these clays. When tripping, the BHA can become stuck in the smaller diameter swelled portions of the borehole. Preventive measures include 1. Avoid long time periods without circulation 2. Be prepared to stop drilling and circulate 3. Plan...

Kick Control

Within the oil industry, there are three recognized kick control procedures. 1 Driller's, 2 Weight, and 3 Concurrent. The selection of which to use will depend upon the amount and type of kick fluids that have entered the well, the rig's equipment capabilities, the minimum fracture pressure in the open hole, and the drilling and operating companies well control policies. Determination of the most suitable and safest method assuming their company policy allows flexibility of procedures...

Overpull

In tight holes or stuck pipe situations, the operator must know how much additional tension, or pull, can be applied to the string before exceeding the yield strength of the drill pipe. This is known as Overpull, since it is the pull force over the weight of the string. For example, in a vertical hole with 12 ppg mud, a drillstring consists of 600 feet of 7.25-inch x 2.25-inch drill collars and 6,000 ft of 5-inch, New Grade E drill pipe with a nominal weight of 19.5 lbs ft and an approximate...

Chapter Casing and Cementing

The weight of a casing joint with threads on both ends and a coupling at one end. 4. AbloluteVolurneigamb 8.34lb gal S.G. ofcomponent 5. 60 fly ash 40 cement 2 additives 6. a Low gel strength, low PV and YP d Chemical make-up similar to the cement 8. Reduce slurry density and viscosity 2102 ft3 559.2 ft3 2661.2 ft3 The total sacks 10. Short pieces of casing used to connect the individual casing joints.

Types of Directional Patterns

The advent of steerable systems has resulted in wells that are planned and drilled with complex paths involving 3-dimensional turns. This is particularly true in the case of re-drills, where old wells are sidetracked and drilled to new targets. These complex well paths are harder to drill and the old adage that the simplest method is usually the best holds true. Therefore, most directional wells are still planned using traditional patterns which have been in use for many years. Common patterns...

Motor Section

Positive Displacement Mud Motors

This is a reverse application of Rene Moineau's pump principle. The motor section consists of a rubber stator and steel rotor. The simple type is a helical rotor which is continuous and round. This is the single lobe type. The stator is molded inside the outer steel housing and is an elastometer compound. The stator will always have one more lobe than the rotor. Hence motors will be described as 1 2, 3 4, 5 6 or 9 10 motors. Both rotor and stator have certain pitch lengths and the ratio of the...

Drillpipe Float Valves

If a kick occurs while a float valve is installed in the drillstring, both fluid and pressure movement up the string will be prevented. It is therefore impossible to read the SIDP when the well is shut-in. If the slow circulation rate SCR is known, it is possible to obtain the SIDP as follows 1. Shut in the well and record the SICP. 2. Start the pumps and maintain them at the SCR. 3. As the pumps are started, adjust the choke to regulate the SICP at the same pressure that was recorded at...

Drill Pipe Grades

There are four common grades of drill pipe which define the yield strength and tensile strength of the steel being used. Grade E, composed of a lower grade of steel, is sometimes referred to as mild steel, because it has the lowest yield strength per unit area. As such, mild steel is generally defined as steel with a yield strength of less than 80,000 psi. As can be seen, Grade E drill pipe has a lower yield strength in psi than the high strength drill pipe grades, however once the yield...

Cement Slurries

Water is added to dry cement to cause hydration and to make a pumpable slurry. To be used correctly, several properties must be known the yield per unit cubic feet per sack , the amount of water required gallons per sack , and its density pounds per gallon . Another important parameter is the cements absolute volume. This is the actual volume occupied by the material the bulk volume includes the open spaces between the cement particles . For example, one sack 94 lbs of cement has a bulk volume...

Summary of Formation Effects

It should be emphasized that in most formations, the rock properties have a minimal effect on the BHAs directional response. In soft to medium soft, isotropic formations, the rock has little influence on directional response and the BHA should follow its theoretical behavior. In medium to hard rocks, which have an appreciable degree of anisotropy, directional tendencies can be significantly affected by formation attitudes and in particular by the effective dip angle of the bedding planes. If...

The Engineers Method

Baker Hughes Pressure Pumping

This is usually a more effective method of killing a kick than the driller's method, if time is not a prime concern Figure 8-5 . Kill mud is pumped into the drillpipe as soon as it is ready, which tends to reduce the high annular pressures associated with gas kicks. The same shut-in procedures are used as outlined in the previous section. When all the calculations have been performed, the mud density is raised immediately to the calculated kill mud density. When the kill mud volume is ready,...

Table Formulas Used In Kick And Kill Procedures

Hydrostatic Pressure psi MW x TVD x 0.0519 Circulating Pressure psi MW x TVD x 0.0519 Pla where Pla Annular Pressure Loss psi Initial Circulating Pressure psi SPR SIDP where SPR System pressure loss at kill rate psi SIDP Shut-in Drillpipe Pressure psi Final Circulating Pressure psi KMW MW x SPR where KMW Kill Mud Density lb gal Kill Mud Weight lb gal MW SIDP TVD x 0.0519 Formation Pressure psi SIDP MW x TVD x 0.0519 Density of influx ppg MW - SICP - SIDP L x 0.0519 where SICP Shut in casing...

Ram Preventers

Ram type preventers have two opposing packing elements that are closed by moving them together. Rubber packing elements again, form the seal. A major difference between these and the annular preventer is that they are designed for specific applications. Rams are designed for a certain size of pipe and will only work on that type of pipe. Also, most ram type preventers are designed to seal in only one direction. They will only hold a pressure exerted from the lower side. Thus they will not...

Adjustable Kick Off Housing

The NaviDrill Mach 1 or 2, can be configured with an adjustable U-joint housing drilling motor suitable for both performance and general directional drilling applications. Steerable mixed rotary and oriented mode operation of the motor is possible for all well paths normally required in conventional or medium radius directional drilling operations. The tilt angle of the AKO can be adjusted from 0 to the maximum design angle. The maximum tilt angle ranges from 2 to 2.75 depending on tool size...

Bearing Systems

The first type of bearing system used with roller cone bits was a non-sealed, roller-ball-friction bearing arrangement, utilizing rollers on the heel of the journal. The primary load, or stress was exerted on these rollers, and drilling fluid was used to lubricate the bearings. Bearing size was maximized, since room for a seal was not required. The bearing surfaces were machined and ground to very close tolerances to ensure dependable service. This type of bearing system is also available with...

Mechanics of Differential Sticking

Even when all precautions are taken, stuck pipe may occur. Should this situation develop, there are still ways in which the INTEQ personnel can be of assistance. To free a differentially stuck drillstring, the driller must overcome the restraining force of the drilling fluid, which is pushing the drillstring against a permeable formation. The drillstring drillpipe or collars will soon become imbedded in the filter cake opposite the permeable zone if corrective action is not taken as soon as the...

Introduction

Baker Hughes INTEQ personnel can be valuable members of the drilling team in diagnosing potential stuck pipe problems. Having access to the drilling information via the DrillByte network , the geological data from the Logging Geologist , and using the right analytical approach, INTEQ personnel can assist the client in keeping stuck pipe problems to a minimum. Effective communication between the logging unit, company-man, directional driller and mud engineer can prevent many stuck pipe...

Jetting

Jetting Bit

Jetting or badgering is a technique used to deviate wellbores in soft formations. The technique was developed in the mid 1950s and superseded the use of whipstocks as the primary deflection technique. Although jetting has subsequently been supplanted by downhole motor deflection assemblies it is still used frequently and offers several advantages which makes it the preferred method in some situations. A special jet bit may be used, but it is also common practice to use a standard soft formation...

Green Cement

A rare occurrence of stuck pipe is one due to soft or green cement. This occurs when the cement is not allowed to set properly, or because of incorrect additives and bottomhole temperature gradients, the cement does not set properly. After the normal time for WOC Waiting On Cement and the drillstring is tripped in to drill out the plugs and float equipment, the cement can flash set when pressure is applied. Preventive measures include 1. Pre-treat the drilling fluid if green cement is suspected...

Neutral Point

The neutral point is usually defined as the point in the drillstring where the axial stress changes from compression to tension. The location of this neutral point depends on the weight-on-bit and the buoyancy factor of the drilling fluid. In practice, since the WOB fluctuates, the position of the neutral point changes. It is therefore quite common to refer to a transition zone as the section where axial stress changes from compression to tension. Drillstring components located in this...

Kick Tolerance

Kick tolerance is defined as the maximum Pore Pressure Gradient that may be encountered if a kick is taken at the present depth, with the present mud density and the well is shut-in, without downhole fracturing occurring. During drilling, kick tolerance must not be exceeded because if a kick occurs there is a considerable chance that an underground blowout will occur when the well is shut-in. A complete description of kick tolerance, with the relevant equations and calculations can be found in...

Downhole Motors

The idea of using downhole motors to directly turn the bit is not a new one. One of the first commercial motors was turbine driven. The first patent for a turbodrill existed in 1873. The USSR focused efforts in developing downhole motors as far back as the 1920's and has continued to use motors extensively in their drilling activity. After 1945, the West focused efforts more on rotary drilling, but field applications for downhole motors has increased spectacularly from the 1980's onwards. A...

Clinging Constant

Turbulent Flow Annulus

Is known as the clinging constant Kj. It represents the proportion of pipe velocity which must be added to fluid velocity in order to find the equivalent or effective velocity, which must be used in the stationary annulus calculation. The effective velocity is numerically greater than the actual fluid velocity, because Va and vp are opposite signs and the clinging constant is negative. For Newtonian fluids, the clinging constant depends only on the annulus diameter ratio. This is not the case...

Workbook

Figure 5-47 Collar strength determination A collar's axial moment of inertia I, is determined by Figure 5-47 Collar strength determination A collar's axial moment of inertia I, is determined by I p 64 x OD4 - ID4 The weight per unit length, W, is calculated from W p 4 p x OD2 - ID2 where p is the density of the steel. Notice that the stiffness is proportional to the fourth power of the outside diameter, while the collar weight is proportional to the square of the outside diameter. This means...

Inadequate Hole Cleaning

Inadequate hole cleaning causes overloading of the annulus. In highly deviated or horizontal wells, this results in the formation of a cuttings bed on the low side of the borehole. Preventive measures include 1. Control the drill rate to ensure the hole is cleaned 2. Circulate bottoms-up until shakers are clean 3. Always check the volume of cuttings coming over the shaker 4. Maintain the correct drilling fluid properties 5. Control the annular velocities 6. Recognize increased overpull 7....

Depth References

During the course of a directional well, there are two kinds of depths Measured Depth MD is the distance measured along the actual course of the borehole from the surface reference point to the survey point. This depth is always measured in some way, for example, pipe tally, wireline depth counter, or mud loggers depth counter. True Vertical Depth TVD is the vertical distance from the depth reference level to a point on the borehole course. This depth is always calculated from the deviation...

Dogleg Capabilities

The dogleg capability for the AKO is variable and is a function of the adjustable U-joint housing angular offset. The range of AKO U-joint housing adjustment, and corresponding dogleg capability for both oriented-only and steerable mixed mode operation, are detailed in the NaviDrill Operations handbook. Using lower DLS and AKO settings, the motor can be rotated and used as a steerable motor. The AKO motor can also be used as a partially stabilized system with bearing housing stabilizer fully...

Preventing Stuck Pipe

If the driller is unable to free the stuck pipe or the force necessary to free the pipe is greater than the force that can be applied by the blocks, then other remedial measures must be used. Normally a lubricating fluid is spotted in the troublesome area and is used to dissolve the filter cake. Spotting procedures and calculations have been mentioned in the Advanced Logging Procedures manual, under Additional Volume Calculations. These spotting procedures are facilitated by pin-pointing the...

Gel Strengthlbs ft secmin

This is a measurement that denotes the thixotropic properties of the mud and is a measurement of the attractive forces of the mud while at rest or under static conditions. As this and yield point are both measures of flocculation, they will tend to increase and decrease together, however a low yield point does not necessarily mean 0 0 gels Gel strength is measured with the viscometer by stirring the mud at high speeds for about 15 seconds and then turning the viscometer off or putting it into...

Undergauge Borehole

When drilling long sections of abrasive formations, the gauge protection on the bit and stabilizers can become so worn it becomes ineffective. Any additional hole that is drilled will be undergauge. Preventive measures include 1. Properly gauge the bit and stabilizers after each run 2. Ream back to bottom if an undergauge hole is suspected 3. Never force a new bit to bottom 4. Select bits with good gauge protection 5 amp 7 feature in roller 5. Carefully run fixed cutter bits after roller cone...

Cost Per Foot Calculations Including Downhole Motors

When downhole motors are used and charged at an hourly rate, they can be included in the cost equation C CRig D tf CBit Moto D C d The following example is a case history. The above equation was used to qualify the savings to an operator in the North Sea when drilling a very hard conglomerate formation with an impregnated diamond bit and a turbine. Calculations were made based on all the bit runs through the conglomerate formation on five different wells. The following values were used for the...

MakeUp Torque

Part of the strength of the drillstring and the seal for the fluid conduit are both contained in the tool joints. It is very important therefore, that the correct make-up torque is applied to the tool joints. If a tool joint is not torqued enough, bending between the box and pin could cause premature failure. Also, the shoulder seal may not be properly seated, resulting in mud leaking through the tool joint, causing a washout. Exceeding the torsional yield strength of the connection by applying...

Bit Technology

The Advanced Logging Procedures workbook contains information on drill bits, IADC classifications and bit grading, and should be reviewed before beginning this chapter. The first successful rolling cutter rock bit was introduced into the oil field by Howard Hughes Sr. in 1909. Over the next fifteen years, the rolling cutter bit was used primarily in hard formation areas. This rolling cutter bit was a two-cone bit with cones that did not mesh, consequently, the bit had a tendency to balled-up in...

Advantages of NDS

Elimination of trips for directional assembly changes, saving rig time More complex well paths can be drilled Wells are drilled more closely to the plan at all times Smaller directional targets can be hit Steerable turbines use the side force method by having an eccentric or offset stabilizer at the lower end of the bearing section at the bottom end of the turbine body, quite close to the bit. The three blade version shown below is the one most commonly used, but a single blade version exists...

Critical Buckling Force

Dawson and Paslay developed the following formula for critical buckling force in drill pipe. I is axial moment of inertia. W is buoyed weight per unit length. r is radial clearance between the pipe tool joint and the borehole wall. If the compressive load reaches the Fcr, then sinusoidal buckling occurs. This sinusoidal buckling formula can be used to develop graphs and tables see pages 4-18 through 4-23 . If the compressive load at a given inclination lies below the graph, then the drill pipe...

Hydrostatic Pressure

System Pressure Drop

As mentioned earlier, this is the pressure created by a column of fluid due to its density and vertical height. This type of pressure always exists and may be calculated whether the fluid is static or flowing. It can be calculated using Hp psi MWx 0.0519 x TVD ft Hydraulic Pressure This is the pressure created or needed to move drilling fluid through pipe. In oil field terms, it is the pressure generated by the mud pump in order to move the drilling fluid from the mud pump around the system and...