Azimuth
In the azimuth system, directions are expressed as a clockwise angle from 0 to 359.99 , with North being 0 . Figure 5-12 The Azimuth System Quadrant Bearings Figure 5-12 The Azimuth System Quadrant Bearings In the quadrant system Figure 5-13 , the directions are expressed as angles from 0 -90 measured from North in the two Northern quadrants and from South in the Southern quadrants. The diagram in Figure 5-14 illustrates how to convert from the quadrant system to azimuth, and vice versa. Figure...
Baker Hughes INTEQ
The relationship between True North and Grid North is indicated by the angles 'a' in Figure 5-9. Convergence is the angle difference between grid north and true north for the location being considered. Figure 5-9 Relationship between True North and Grid North Figure 5-9 Relationship between True North and Grid North The reference meridians are 6 degrees apart, starting at the Greenwich meridian, which means the world is divided into 60 zones. The zones are numbered 0 to 60 with zone 31 having...
Multiple wells from offshore structures
The most common application of directional drilling techniques is in offshore drilling. Many oil and gas deposits are situated well beyond the reach of land based rigs. Drilling a large number of vertical wells from individual platforms is both impractical and uneconomical. The obvious approach for a large oilfield is to install a fixed platform on the seabed, from which many directional boreholes can be drilled. The bottomhole locations of these wells are carefully spaced for optimum recovery....
Additional ReviewReading Material
EXLOG, MS-3026 Theory And Applications Of Drilling Fluid Hydraulics Baker Hughes INTEQ, Drilling Fluids Manual, 1991 API, The Rheology of Oil-Well Drilling Fluids, Bulletin 13D,2nd Edition, May 1985 API, Recommended Practice for Drilling Mud Report Form, Report 13G, 2nd Edition, May 1982 Chilingarian, G.V. and Vorabutr, P., Drilling and Drilling Fluids, Elsevier Science Publishers, 1983 Bourgoyne Jr., Adam, et al Applied Drilling Engineering, SPE Textbook Series, Vol. 2, 1986 Moore, Preston...
Workbook
Figure 5-15 Type 1 Build and Hold Figure 5-15 Type 1 Build and Hold Build-up section which may have more than one build up rate Tangent section Deep wells with large horizontal displacements Moderately deep wells with moderate horizontal displacement, where intermediate casing is not required Features There are several variations Shallow KOP - Build, hold amp drop back to vertical Build-up section - Build, hold, drop amp hold illustrated above Tangent section - Build, hold amp continuous drop...
Junk in the Borehole
Junk is a foreign object in the borehole, which is not meant to be there. Since the clearance between casing and collars stabilizers is not great, even a small piece of junk can stick the drillstring. Preventive measures include 1. Ensure downhole tools are in good condition 2. Inspect downhole tools regularly 3. Be careful when working around the rotary table 4. Leave the hole covered when the drillstring is out of the borehole 5. Install drillpipe wipers whenever possible If junk sticking is...
Bullheading
This is defined as pumping fluid into the well without circulation back to the surface. The fluid can be pumped down the drillpipe, down the annulus, or both. In most instances this will result in formation fracturing. This will occur at the weakest point, which is usually the formation near the last casing shoe. Obviously, in underground blowouts or wells with lost circulation, bullheading can prove useful since the fracture or loss zone already exists. Wells with short open hole sections and...
Baker Hughes INTEQ Jwz
7. Determine what specifications govern the writing There is an FWR format and it usually uses a canned selection of questions statements which are to be answered. 8. Determine deadlines for each stage of the writing task Normally, rough drafts of the FWR are required after each casing point and at the end of the well. These deadlines also include when the final version of the report is due, when the illustrations or plots prints are due, and when all are to be delivered to the client. 9....
Introduction Smr
Drillstrings weigh less in weighted fluids than in air due to a fluid property known as buoyancy. Therefore, what is seen as the hookload is actually the buoyed weight of the drillstring. Archimedes's principle states that the buoy force is equal to the weight of the fluid displaced. Another way of saying this is that a buoy force is equal to the pressure at the bottom of the string multiplied by the cross sectional area of the tubular. This is due to the fact that the force of buoyancy is not...
Workbook Xaw
Figure 5-31 BHA using the fulcrum principle. Figure 5-31 BHA using the fulcrum principle. The rate of build will be INCREASED by the following Increasing the distance from the near-bit stabilizer to the first string stabilizer Increase in hole inclination Reduction of drill collar diameter Reduction in flow rate in soft formations The distance from the near-bit stabilizer to the first string stabilizer is the main design feature in a fulcrum assembly which will affect the build rate. The build...
Drilling Fluid Report
One of the most important reports at the wellsite is the daily drilling fluid report, or mud report. In addition to containing basic well and rig information, chemical inventory and mud system costs, the mud report will contain a list of the fluid properties of the mud system. To maintain the required properties, certain tests are conducted on the drilling fluid. The most important are listed below. The density of the drilling fluid is important to maintaining well control. As mentioned...
Chapter Directional Drilling
1. a. Multiple wells from offshore platforms 2. True North - this is the direction of the geographic north pole, which lies on the Earth's axis of rotation Magnetic North - This is the direction of the magnetic north pole, which lies in northern Canada. Grid North - the northern direction as depicted on a flat surface i.e. a map S64.75E 115.25 N35E 35 S88.75W 268.75 N66.5W 293.5 S22.25E 157.75 N35.5W 324.5 S89E 91 N71.5E 71.5 S25.5W 205.5 N3.75W 356.25 S11.5E 168.5 4. Advantage Simple piece of...
Planning a nudge program
The directions in which the wells are nudged'' should be chosen to achieve maximum separation. Wells may not necessarily be nudged in their target directions. Nudges will not only be shown on the individual well plans for each well, but a structure plot will also be drawn which will show well positions at the surface casing point after the nudge. On multi-well projects particularly offshore there are small distances between slots. To eliminate the risk of collisions directly beneath the...
The Drillers Method
When a kick occurs, the normal procedures is as follows 1. Pick up the kelly and note the position of tool joints in relation to the drilling spools. 4. Close the annular preventer or ram preventers. 7. Record the SIDP and SICP when they stabilize. Once the well is shut-in, it is necessary to calculate the kill mud density, initial and final circulating pressures, and the kick fluid gradient. If the kick fluid is gas, the bubble may start to percolate up the annulus. this will cause a slow rise...
Summary and Recommended Practices
The safest approach to designing and using a pendulum assembly is to concentrate on producing a side force at the bit on the low side of the hole. This is achieved by running an assembly where the pendulum portion will be as stiff and straight as possible. It is also desirable that the section immediately above the first string stabilizer be stiff and straight and that a second string stabilizer be within 30 feet of the first. Omit the near-bit stabilizer when azimuth control is not a concern...
End Of Manual Return Exercises 1
1. Name the classifications of drilling fluid systems. 2. Excess filter cake can lead to four basic problems. Name them. 3. Give the generalizations that have been made concerning cuttings transport. 4. Compute the volume and density of a mud composed of 25 lb of bentonite, 60 lb of barite, and 1 bbl of fresh water. 5. There are 500 barrels of an 18.0 lb gal mud with the following composition Oil 51 , Water 9 , Solids 40 2 The fluid type and amount to increase the oil ratio to 90 10. 3 The...
Bearing Section 1
Usually, thrust bearings are made up of rubber discs Figure 5-24 which are non-rotating being fixed to the outer housing of the tool and rotating steel discs attached to the central rotating shaft. Long bearing sections known as cartridges are used for long life in tangent or straight hole drilling sections. These are changeable at the rigsite. If the bearings wear past the maximum point, considerable damage can be inflicted as the steel rotors will crash into the stators below. Figure 5-24...
SelfCheck Exercises 1
1. What do the threaded and coupled weight standards refer to 2. Three common API grades of casing and their associated tensile strengths are 3. After the initial calcareous and argillaceous cement materials are mixed and baked in a kiln at 2800 F, the resulting mixture is known as 4. What formula is used to calculate the absolute volume of cementing materials 5. An example of a slurry mixture is 60 40 2. What do these three numbers refer to 6. What are the ideal properties of a drilling fluid...
Imposed Pressure
These are external pressures which are imposed into the well. Since the well is open to the atmosphere, the well must be shut-in for there to be an imposed pressure. This type of pressure will always be felt uniformly throughout the shut-in well. Imposed pressures originate from 1. the pumps i.e. when testing a casing shoe 2. the formation i.e. when the well kicks Assume that the well in Exercise 1-4 on page 1-21 is shut in annular preventer amp choke are closed and a small amount of mud is...
Effective Dip Angle in a Deviated Hole
In a directional well, the effective dip angle is the angle at which the bit strikes the bedding planes. Figure 5-52 At high dip angles, deviation tendency is down-dip. Figure 5-53 Hole inclination 30 Real dip angle 35 Effective dip angle 30 35 65 There will be a down-dip deviation force. Figure 5-53 Hole inclination 30 Real dip angle 35 Effective dip angle 30 35 65 There will be a down-dip deviation force. Figure 5-54 Hole inclination 0 Effective angle of dip equals real dip angle 35 There...
Hsi A
If the area of the bit is not given, it can be calculated using The hydraulic horsepower equation is the same Pb x Q 1714 , however in fixed cutter bits, resistance to fluid flow is created by the diamonds, nozzles, flow area restrictions, cuttings and the uneven hole pattern. Pressure losses at the bit are calculated using
Nozzling the Jetting Bit
1. Use a specialized jet bit with a large extended nozzle in place of one of the cones. 2. Fit one large and two small nozzles in a conventional tri-cone bit. 3. Blank off one nozzle of a conventional bit to divert the flow through the other two. Flow through two jets may be desirable in large hole sizes e.g. 17-1 2 because of the large washout required to deflect the bit and near bit stabilizer. Both A and B work well in most hole sizes which are commonly jet drilled. B is the most common...
Nudging
The technique of nudging is used on platforms in order to spread out conductors and surface casings, which minimizes the chance of a collision. Basically, when the hole for surface casing is drilled, some angle is built at a low rate e.g. 17100' in the chosen direction. In addition to spreading things out, other reasons for nudging are to drill from a slot located on the opposite side of the platform from the target, when there are other wells in between to keep wells drilled in the same...
Breakeven Cost Analysis
Before deciding to run the more expensive bits insert, PDC, or diamond through a zone previously drilled with a lower priced bit mill tooth . It is frequently desirable to define, as precisely as possible, the required performance of the next bit. This analysis may range from a simple cost-per-foot comparison, to more complicated and detailed investigations involving drilling fluids, required operating conditions and other variables. Since the ultimate goal of the drilling operation is to make...
DTU Basic Components
Bypass Valve with box connection Navi-Drill motor section - Mach 1 or 2 Double tilted U-joint housing Upper bearing housing with stabilizer UBHS Only the DTU housing, universal joint, and upper bearing housing components will be discussed other components are standard Navi-Drill parts. Navi-Drill performance or operating specifications are not altered by the addition of these two special components. The DTU steerable motor is shown in Figure 5-57.
The Fulcrum Principle
An assembly with a full gauge near-bit stabilizer, followed by 40 to 120 feet of drill collars, before the first string stabilizer, or no string stabilizer at all, will build angle when weight-on bit is applied. As illustrated in Figure 5-31, the collars above the near-bit stabilizer bend, partly due to their own weight and partly because of the applied WOB. The near-bit stabilizer acts as the pivot, or fulcrum, of a lever and the bit is pushed to the high side of the hole. The bit therefore...
Underground Blowout
This is an uncontrolled flow of formation fluids from a high pressure zone into a lower pressure zone. The loss of drill pipe pressure with changes in annular pressure, the loss of large volumes of drilling fluid, or the total loss of drilling fluid returns, characterizes underground blowouts. A common cause is the fracturing of formations below the casing shoe by excessive annular pressures. If the flow is not too severe, it may be possible to pump LCM in a light fluid, or a gunk squeeze down...
Navigation Drilling Systems
Most conventional directional drilling operations will require extra trips to change the BHA for directional control. In addition, bit performance can be reduced by those same conventional deflection techniques. Several methods exist for continuously controlled directional drilling using steerable downhole motors. These methods are based upon tilting the axis of the bit with respect to the axis of the hole to creating a side force at the bit. If the drill string, and the body of the motor, is...
Kick Control Methods
All kill procedures require data concerning drillstring geometry, hole geometry, mud density, pump rates, pressure losses, and fracture pressure. Important data that is required prior to initiating kill procedures include 1. Circulating pressure at kill rate 2. Surface to bit time at kill rate in strokes and minutes 3. Bit to surface time at kill rate in strokes and minutes 4. Maximum allowable annular pressure 5. Formula for calculating the kill mud density 6. Formula for calculating the...
MD x Q
Since PDC bits are formation specific best used in plastic formations , the formation characteristics will determine the hydraulic energy required. The drilling fluid will dictate the HSI, for water-based drilling fluids it will be between 2.5 and 4.5, while for oil-based drilling fluids it will be between 1.5 and 3.0. The HSI, calculated at the jet nozzle orifices, will have several characteristics which will directly affect hydraulic energy 1. the fluid velocity decreases rapidly once it...
Downhole motor and bent sub
A common method of deflecting wellbores is to use a downhole motor and a bent sub. As illustrated in Figure 5-29, the bent sub is placed directly above the motor and the bent sub which makes this a deflection assembly. Its lower thread on the pin is inclined 1 - 3 from the axis of the sub body. The bent sub acts as the pivot of a lever and the bit is pushed sideways as well as downwards. This sideways component of force at the bit gives the motor a tendency to drill a curved path, provided...
Catenary Curve Well Plan
One suggestion for an efficient well path for directional wells would be to plan the well as a continuous smooth curve, all the way from KOP to target. This is the catenary method. A catenary curve is the natural curve that a cable, chain or any other line of uniform weight assumes when suspended between two points. A similar suspension of drill string would also form a catenary curve. Proponents of the catenary method argue that it results in a smoother drilled wellbore, that drag and torque...
Annular Pressure Losses
Hydraulic calculations continue with a determination of the amount of pressure lost in the annulus. Assuming laminar flow, the Power Law Model pressure loss equation is Pi kX-L f1-6x Vx G n 300 dl-d2 x t 0 where k Consistency index L Length of section feet dj Hole or Casing I.D. inches d2 Pipe or Collar O.D. inches V Annular Velocity in Section ft min Fluid velocity in the annulus is determined by using where D1 hole or casing I.D. inches D2 pipe or collar O.D. inches A geometric factor is used...
Relationship Between Dip Angle and Deviation Force
Based on the preferential chip formation theory, the graph shown below has been derived from experimental work. Figure 5-49 Maximum deviation force as a function of formation dip. Figure 5-49 Maximum deviation force as a function of formation dip. The effective dip angle is the angle at which the bit strikes the bedding plane. The graph predicts that when the effective dip angle is less than 45 , the direction of the deviation force is up-dip. When the effective dip angle is greater than 45 the...
Calculating Critical Buckling Force
Calculate the critical buckling load for 4.5-inch grade E drill pipe with a nominal weight of 16.6 lb ft approximate weight 17.98 lb ft tool joint OD 6.375 inches from API RP7G, Table 2.10 in an 8.5-inch hole at 50 inclination. 1. Young's modulus, E, for steel is 29 x 10 psi 4.5-inch drill pipe with a nominal weight of 16.6 lbs ft has an ID of 3.826 inches. This information can be found under NewDrill Pipe Dimensional Data in the API RP-7G. Table 2.1 3. The approximate air weights for different...
The Pendulum Principle
This was the first directional control principle to be formulated and was originally analyzed for slick assemblies drilling straight holes. We shall concentrate on pendulum assemblies used in deviated wells. The portion of the BHA from the bit to the first string stabilizer hangs like a pendulum and, because of its own weight, presses the bit towards the low side of the hole. The major design feature of a pendulum assembly is that there is either no near-bit stabilizer or an undergauge near-...
Sidetracking
Sidetracking out of an existing wellbore is another application of directional drilling. This is done to bypass an obstruction fish in the original wellbore, to explore the extent of a producing zone in a certain sector of a field, or to sidetrack a dry hole to a more promising target. Wells are also sidetracked to access more reservoir by drilling a horizontal hole section from the existing well bore.
Plastic Viscosity
Shear rate is the rate of change as the fluid layers move past one another per unit distance, and is measured in reciprocal seconds i.e. ft sec ft and is usually written as seconds-1. To convert the dial reading to shear stress, the dial reading is multiplied by 1.067 to give a reading in lb 100ft2. The units of viscosity are poise or centipoise 1 100 poise and is derived as follows Viscosity poise F A V H where F Force dynes A Area cm2 This produces viscosity as Dynes sec cm2 or poise. The...
Target ROP with a Downhole Motor
The Baker Hughes INTEQ engineer decides the only way to persuade the client to use a motor is to offer a performance deal based on the cost per foot calculated above. The target ROP is calculated as follows. Standard hourly rate for motor 220 hr including engineer Target cost for interval 4,550 ft x 147.62 ft Target drilling costs 671,650 - 2000 x 26 50,900 or, 568,750 T arget drilling hours ,-- - F --f--- Target drilling hours 2 000 220 256.2 4 550 After consulting database records, the INTEQ...
Permanent Casing Whipstock
The Permanent Casing Whipstock Figure 5-26 is designed to remain permanently in the well. It is used where a window is to be cut in casing for a sidetrack. The casing whipstock can be set using a Baker Model D Packer. A special stinger at the base of the whipstock slips into the packer assembly, and a stainless steel key within the packer locks the whipstock's anchor-seal and prohibits any circular movement during drilling. The normal procedure is to orientate the system and then set the...
Bingham Plastic Model
The Bingham model is defined by the relationship Shear Stress Yield Stress Plastic Viscosity x Shear Rate The major difference between this and Newtonian fluids is the presence of a Yield Stress or Yield Point which is a measure of the electronic attractive forces in the fluid under flowing conditions . No bulk movement of the fluid occurs until this yield stress is overcome. Once the yield stress is exceeded, equal increments of shear stress produce equal increments of shear rate. Flow Curve...
Journal Angle
Journal angles are different for each type of formation Soft Formations Journal angle 33o - this allows a cutter profile which accentuates cutter action and permits greater tooth depth. Journal angle 34o to 36o , to decrease cutter action. Hard Formations Uses a large journal angle 39o , to minimize cutter action. 0 Journal 15 Journal 30 Journal 36 Journal Figure 3-1 Journal Angles in Roller Cone Bits The idea of interfitting teeth Figure 3-2a , makes it possible to have large bit parts, and...
PDC Bit Operating Parameters
PDC bits do not have the benefit of the self fluid-cleaning action between rows of teeth like roller cone bits, so they must rely on the bit's hydraulics to flush the cuttings from under the bit to prevent balling. This is accomplished with strategically positioned converging-diverging nozzles which maximize cleaning while minimizing erosion of the body near the nozzle area. Optimum hydraulic range is between 2.0 to 4.0 hydraulic horsepower per square inch. The interchangeable jet nozzles come...
BHA Weight WeightOnBit
One important consideration in designing the BHA is determining the number of drill collars and heavy-weight pipe required to provide the desired weight-on-bit. When drilling vertical wells, standard practice is to avoid putting ordinary drill pipe into compression recommended by Lubinski in 1950 . This is achieved by making sure that the buoyed weight of the drill collars and heavy-weight pipe exceed the maximum weight-on-bit. This practice has also been adopted on low inclination,...
Checklist For Technical Writing
1. Before beginning, classify the technical writing task The Final Well Report FWR , and in particular the Drilling and Engineering section, is an engineering report. 2. Determine the desired length of the written work The length of the FWR is determined by company recommendations, modified by the amount of data information to be presented. 3. Define the reason for writing the piece The FWR is used to report findings, conclusions and recommendations concerning the well that was drilled....
Tripping on a fixed rig
Once the warning signs of a kick have been observed, the top tool joint should be set in the slips. 1. An open, full-opening safety valve should be installed onto the pipe. This is easier to install than a float valve, because any flow up the pipe will tend to close the float during installation a float valve can always be added to the string later to allow stripping back to bottom . 2. The safety valve should be closed, then the annular preventer is closed. 3. Pick up, and make up the kelly....
Standard removable Whipstock
The Standard Removable Whipstock is mainly used to kick off wells, but can also be used for sidetracking. It consists of a long inverted steel wedge which is concave on one side to hold and guide the drilling assembly. It is also provided with a chisel point at the bottom to prevent the tool from turning, and a heavy collar at the top to withdraw the tool from the hole. It will usually be used with a drilling assembly consisting of a bit, a spiral stabilizer, and an orientation sub, rigidly...
Key Seating
Key seats are the result of the drillstring wearing an additional hole into the side of the borehole. This extra hole will generally have the I.D. of the drillpipe's tool joints and the drill collars will not pass through this extra hole when tripping out. Preventive measures include 5. Minimize the length of rathole below casing 6. Have a surface jar on location 7. If the problem is recognized, cure it before drilling ahead If the drillstring becomes key seated, the drillstring should be...