Control Fluid Circuit
In addition to the control fluid circuits used to operate stack functions such as ram or annular preventers, the control system must also perform other functions such as control of subsea regulators, provide readback pressures, latch unlatch the subsea control pods and charge the subsea accumulators. Fig 9.4 shows a typical control fluid circuit. The hydraulic fluid is mixed, pressurised and stored in accumulator bottles by the hydraulic power unit. A pilot operated accumulator isolator valve...
Automatic Opening To Diverter Lines As Bag Closes 1
Figure 6.3.3 Example diverter with annular packing element Figure 6.3.3 Example diverter with annular packing element Figure 6.3.4 Example diverter with insert - type packer Figure 6.3.4 Example diverter with insert - type packer Figure 6.3.5 Example diverter with rotating stripper Figure 6.3.5 Example diverter with rotating stripper Figure 6.3.6 Example diverter systems - Integral sequencing Figure 6.3.6 Example diverter systems - Integral sequencing
Balance Of Pressures
Once the well is shut-in providing nothing has broken down, the pressures in the well will be in balance. What is lacking in hydrostatic head of fluid in the well is now being made up by surface applied pressure on the annulus and on the drill pipe. Providing the bit is on bottom and the string is full with a known mud density this allows us to determine what the formation pressure is and hence what kill mud weight is required to achieve balance. On the drill pipe side of the U-tube. Figure 5.1...
The Drillers Method
In the Driller's Method, the kick is circulated out of the hole using the existing mud weight. The mud weight is then raised to the required level and circulated around the well. Two complete circulations are thus required, as a minimum, for this method. Since it deals separately with the removal of the kick and the addition of kill weight mud, it is generally considered to be the simplest of well control methods, and it requires least arithmetic. However, this results, in the well being...
Secondary ram shaft seal
1 Manual-lock piston in open position Locking shaft 2 Manual-lock piston in closed and locked position Locking shaft 2 Manual-lock piston in closed and locked position 2 Poslock piston in closed position 3 Manual-lock piston in closed position 3 Manual-lock piston in closed position
Workshop
1. Convert the following mud densities into pressure gradients. 2. Convert the following gradients into mud densities. 3. Calculate the hydrostatic pressure for the following. a. 9.5 ppg mud at 9000ft MD 8000 ft TVD _ b. 15.5 ppg mud at 18000ft TVD 21000ft MD _ c. 0.889 psi ft mud at 11000ft MD 9000ft TVD _ 4. Convert the following pressures into equivalent mud weights in PPG. c. 12000ft MD 10500ft TVD with 9000 psi High bottom hole temperatures could affect the hydrostatic pressure gradients...
Special Features
Flat doors simplify ram changes. To change the rams, apply opening hydraulic pressure to move the rams to the full open position. Remove the door cap screws and swing the door open. Remove the ram from the ram shaft and replace it. It is not necessary to apply closing hydraulic pressure to move the rams inward to clear the door. Door seals on most sizes have a hard backing moulded into the rubber. This fabric and phenolic backing prevents extrusion and pinching at all pressures to assure long...
Inside Bops
The drill pipe float valve and the flapper type of back pressure valve, serve essentially the same purpose, but differ in design. These valves provide instantaneous shut-off against high or low back pressure and allow full fluid flow through the drill string. Another advantage is that it prevents cuttings from entering the drill string, thus reducing the likelihood of pulling a wet string. Abnormal pressures and anticipated subnormal pressure zones should be the deciding factor regarding what...
Close Function
In Fig 9.3a one of the BOP rams is being closed using the drillers master control panel. Pushing the 'close' button on this panel actuates the solenoid valves on the hydraulic manifold thus allowing air pressure to move the pilot control valve to the 'close' position. The solenoid valve on the right in the diagram vents the other side of the air cylinder. With the pilot control valve in the 'close' position, pilot fluid at 3000 psi is sent down the umbilical to the RAMS CLOSE SPM valve in the...
Figure 1
Figure 6.3.9 HYDRIL ANNULAR PREVENTER - TYPE MSP - 2000 PSI Figure 6.3.9 HYDRIL ANNULAR PREVENTER - TYPE MSP - 2000 PSI 1. Will close on open hole and hold 2000 psi but not recommended . 2. Primary usage is in diverter systems. 3. Automatically returns to the open position when closing is released. 4. Sealing assistance is gained from the well pressure. 5. Greater stripping capability of the packing unit since fatigue wear occurs on the outside of the packing unit.
Kick Tolerance Exercise
A well has a TVD of 14500 ft with the casing shoe at 13200 ft TVD. The fracture gradient is 0.87 psi ft and the current mud is 15.3 ppg. There is 700 ft of 6 1 2 OD drill collar and the open hole diameter is 8 1 2, with 5 drill pipe. 1 Calculate the kick tolerance if the well is shut-in with the current mud and a SIDPP of 570 psi. 2 Calculate the kick tolerance for a swabbed kick when the mud weight is equivalent to the formation pore pressure. 1 MAASP Gfrac - GM x DShoe GM 15.3x 0.052...
h Max MAASP
mud gradient psi ft influx gradient psi ft Gfrac - Gm x Ds psi formation fracture gradient at the shoe psi ft pressure profile in annulus at shut-in. when top of gas is circulated to casing shoe, by 'drillers method'. maximum tolerable length of expanded gas influx at shoe H pressure profile in annulus at shut-in. NB. Well geometry assumed to be constant DEFINITION 1 for a kick taken while drilling into a high pressure formation. Kick Tolerance is the maximum allowable influx volume, for a...
Pod Select Valve
ACCUMULATOR psi REGULATOR psi VENT psi Figure 9.2 SUBSEA CONTROL SYSTEM - BLOCK DIAGRAM ACCUMULATOR psi REGULATOR psi VENT psi Figure 9.2 SUBSEA CONTROL SYSTEM - BLOCK DIAGRAM SECTION 9 SUBSEA BOP CONTROL SYSTEMS amp MARINE RISER SYSTEMS The power fluid is routed to the subsea control pod selected by the pod selector valve which is located in the central hydraulic control manifold. The line to the non-selected pod is vented. When power fluid reaches the pod, it is combined with fluid stored at...
Test Plugs And Test Joints
7.A.15 Test Plugs. Several makes of test plugs are available for testing preventer stacks. The testing tool arrangement should provide for testing the bottom blowout preventer flange. Test plugs generally fall into two types, hanger type and cup type. a. The hanger type test plug has a steel body with outer dimensions to fit the hanger recess of corresponding types of casinghead. An O-ring pressure seal is provided between the tester and the hanger recess refer to Figs 7.A.1 and 7.A.2 . The...
Increase In Cutting Size And Shape
In transition zones or in abnormally pressured shales sandy shales and bedding sand streaks the shales break off and fall into hole because of under balanced condition pore pressure greater than mud hydrostatic pressure . Water wetting may further aggravate this problem. Changes in the Shape of Shale Cuttings can occur as an underbalanced situation is developing. The particles are often larger and may be sharp and angular in the transition zone. Extra fill on bottom may coincide with the trend...
Profile of Circulating and Annular Pressure While Killing by Drillers Method 1
Determination of Initial Circulating Pressure If no slow circulating rate pressure has been taken, then the initial circulating pressure can be determined using the start-up procedures described in the circulations of the Driller's Method. Where the casing pressure has been held constant while the pumps are brought up to a kill rate, the drill pipe pressure reading will be the initial circulating pressure. WARNING the existence of a predetermined kill rate gives rig personnel a wrong impression...
Accumulative Volumes
After 15' stripped pressure at 460 psi After 15' stripped pressure at 510 psi After 15' stripped pressure at 560 psi After 15' stripped pressure at 460 psi After 15' stripped pressure at 510 psi After 15' stripped pressure at 560 psi Allow casing pressure to increase to calculated Pchoke pressure while stripping first stand, then hold casing pressure constant by bleed off at choke. Note The casing pressure may not rise straight away because the gas has to be compressed. It may take 2 - 3 stands...
The Hard Shutin Procedure On A Floating Rig
1. When any indication is observed while drilling that the well maybe flowing, stop rotating the drill string, raise drill string with pumps running and space out for hang off rams. 2. Stop pumps and check for flow, if positive 3. With compensator at mid-stroke close annular or pipe rams. 4. Open fail-safe valves on the choke line. 5. Call supervisors and commence plotting a graph of shut in drill pipe pressure. Check pit volume gain. 6. If rams have been closed then reduce manifold pressure,...
WORKSHOP Dim
The following questions 1-5 refer to the first stage of the Drillers Method. 1. A well was shut-in on a kick that occurred whilst drilling. During the first circulation of the Drillers Method, the choke operator maintains a constant drill pipe pressure at a constant pump speed. 2 . Referring to the question above, the choke operator has not taken into account the large volume of the surface lines, i.e. from the pump to the rig floor. This will result in a. An increase in bottom hole pressure b....
Subsea Bop Control Systems Introduction
Every component in a blowout preventer assembly is operated hydraulically by moving a piston up and down or back and forth. Thus the function of a BOP control system is to direct hydraulic fluid to the appropriate side of the operating piston and to provide the means for fluid on the other side of the piston to be expelled. On land, jack-up or platform drilling operations the control of the BOP is easily achieved in a conventional manner by coupling each BOP function directly to a source of...
Early Warning Signs
The alertness in determining early warning signs in well control is of the upmost importance to wellbore safety. Careful observance and positive reaction to these signs will keep the well under control and prevent the occurrence of a well flow situation. The various signs that have been recorded as early warning indicators are not consistent in all situations. The signs however may have to be used collectively as one indicator may not accurately provide the warning of getting into an unbalanced...
The Fast Shutin Procedure On A Floating Rig
1. When any indication is observed while drilling that the well maybe flowing, stop rotating, raise drill string with pumps running and space out for hang off rams. 2. Stop pump and check for flow, if positive 3. Open fail-safe valves on the choke line. 4. With compensator at mid-stroke, close annular. 5. Call supervisors and commence plotting a graph of shut in drill pipe pressure, check pit volume gain. 6. Close hang off rams with reduced pressure, reduce annular pressure, slack off and land...
Graphical Example Of A Volumetric Bleed
5.5.5 Figure 5.11 shows what is happening to the gas in the well. 10 bbls 10 bbls 12.3 bbls 15.9 bbls 18.5 bbls 22.1 bbls 10 bbls 10 bbls 12.3 bbls 15.9 bbls 18.5 bbls 22.1 bbls Gas volume in bbls at the end of each mud bleed. Clearly the description outlined is simplified. Four bleeds are shown. Depending upon the size of the volume bled and the well depth more or less bleeds may be required than illustrated here. 1. Bleed mud at constant choke pressure using the manual choke. Ensure crew...
Increase In Trip Connection And A Background Gas
Return mud must be monitored for contamination with formation fluids. This is done by constantly recording the flowline mud density and accurately monitoring gas levels in the returned mud. Gas cut mud does not in itself indicate that the well is flowing gas may be entrained in the cuttings . However, it must be treated as early warning of a possible kick. Therefore pit levels should be closely monitored if significant levels of gas are detected in the mud. An essential part of interpreting the...
WORKSHOP a Surface
preventer J Note The well will be killed using the left hand automatic choke. To mud gas separators, pits and diverter lines To mud gas separators, pits and diverter lines i To mud gas separators, pits and diverter lines Remotely operated choke - right hand IP Positive Closing Choke i To mud gas separators, pits and diverter lines Remotely operated choke - right hand IP Positive Closing Choke Questions 1-4 refer to the diagram above. The valves shown are numbered 1 to 15. 1. If all of the above...
Examples Of Leakoff Test Plot Interpretation
In non-consolidated or highly permeable formations fluid can be lost at very low pressures. In this case the pressure will fall once the pump has been stopped and a plot such as that shown in Fig 1.14a will be obtained. Figs 1.14b and 1.14c show typical plots for consolidated permeable and consolidated impermeable formations respectively. CUMULATIVE VOLUME CUMULATIVE VOLUME c Consolidated Impermeable Formations c Consolidated Impermeable Formations
Redundancy
The two subsea control pods are functionally identical. When a pilot control valve rams close for example is operated on the hydraulic control manifold a pilot signal is sent down both umbilicals so that the associated SPM valve in each pod 'fires'. If the pod selector valve is set on yellow then power fluid is sent only to this pod and it is only through the SPM valve in this pod that the fluid will reach the ram operating piston. The pod selection has no effect on the pilot system. Once the...
SURFACE TEST PRESSURE PSI Eaw
NOTE Commence plotting pressure and pumped volume after SECTION 1 FUNDAMENTAL PRINCIPLES OF WELL CONTROL 1.8 MAXIMUM ALLOWABLE ANNULAR SURFACE PRESSURE - MAASP. The leak-off test was used to determine the strength of the formations below the casing shoe. The Formation Breakdown Pressure an applied surface pressure hydrostatic pressure of mud in the casing The applied surface pressure at which leak-off occurred is the maximum allowable annular surface pressure with the mud weight in use at that...
Soft Shutin Procedure While Drilling On A Floating Rig
1. When any indication is observed while drilling that the well maybe flowing, stop rotating the drill string, raise drill string with pumps running and space out for hang off rams. 2. Stop pumps and check for flow, if positive 3. Open fail-safe valve, open the choke line. 4. With compensator at mid-stroke, close annular. 5. Close choke if the choke is not a positive closing choke then close a valve downstream of choke. 6. Call supervisors and commence plotting a graph of shut in drill pipe...
DRILL PIPE CHOKE MANIFOLD Ivn
Ph 5200 psi in annulus PUMP AT KILL RATE HOLDING CONSTANT CHOKE MANIFOLD PRESSURE CHANGE IN BHP 200 psi increase SECTION 1 FUNDAMENTAL PRINCIPLES OF WELL CONTROL To eliminate this problem, two methods exist. First, by reducing choke manifold pressure by an amount equal to a known CLFL adjusting choke manifold pressure to SICP -CLFL , the effect of the CLFL is negated. This is accomplished by reducing the original SICP by the amount of CLFL while bringing the pumps to speed see Figure 1.23 ....
Fundamental Principles Of Well Control
The objectives of this section are to introduce the Fundamental Principles of Well Control. The function of Well Control can be conveniently subdivided into three main categories, namely PRIMARY WELL CONTROL, SECONDARY WELL CONTROL and TERTIARY WELL CONTROL. These categories are briefly described in the following paragraphs. It is the name given to the process which maintains a hydrostatic pressure in the wellbore greater than the pressure of the fluids in the formation being drilled, but less...
Increase In Drilling Rate Of Penetration Drilling Break
When drilling ahead and using consistent drilling parameters, as the bit wears, a normal trend of decrease penetration rate should occur. If the differential pressure between the hydrostatic pressure of the drilling fluid and formation pore pressure decreases, an increase in the drilling rate occurs as the chip hold down effect is reduced. A general and consistent increase in penetration rate is often a fairly good indicator that a transition zone may have been penetrated. A rapid increase in...
Secondary Seal
The secondary seal is activated by screwing down on the piston which forces plastic through the check valve and into the space between the two swab cup seals. Further piston displacement causes pressure to build up between the swab cups, forcing them to flare out and provide a seal. When the pressure exerted by the plastic packing reaches the proper valve, additional displacement of the piston will overcome the spring tension in the relief valve and plastic packing will begin to extrude from...
GASKETS SEALS AND WELLHEADS API Type R Ring Joint Gasket
The type 'R' ring joint gasket is not energised by internal pressure. Sealing takes place along small bands of contact between the grooves and the gasket, on both the OD and ID of the gasket. The gasket may be either octagonal or oval in cross section. The type 'R' design does not allow face-to-face contact between the hubs or flanges, so external loads are transmitted through the sealing surfaces of the ring. Vibration and external loads may cause the small bands of contact between the ring...
Gas Kick In Horizontal Section
a Gas will not migrate if hole angle is 90 degrees or greater. b Gas will not migrate if it is dissolved in oil based mud. c Gas maybe trapped in undulations or washouts or in hole sections which are greater than 90 degrees. d If gas cannot be removed from inverted sections then consider bullheading gas into formation. e Slow circulating rates which give a flow rate greater than 130 ft min while circulating gas out of horizontal section should be considered. Flow rates lower than this may not...
U II Blowout Preventer
The Cameron U II BOP takes all of the features of the U BOP and adapts them for subsea use in the 18-3 4-10,000 and 15,000 psi WP sizes. Like all other Cameron preventers, the rams in the U II BOP are pressure-energized. Wellbore pressure acts on the rams to increase the sealing force and maintain the seal in case of hydraulic pressure loss. Seal integrity is actually improved by increased well bore pressure. Other features of the U II BOP include Internally ported hydraulic stud tensioning...
Shallow Gas And Diverting Procedure On A Floating Rig
1. Shallow gas sand lenses are normally completely enveloped in mud stone and tend to be highly porous, permeable and relatively unconsolidated. These lenses maybe normally pressured, but if they are lying at an inclination they may be overpressured. 2. Shallow gas kicks happen when drilling into a sand lens and are generally caused by loss of hydrostatic head due to one or a combination of the following. a Overloading the annulus with cuttings which may cause losses. b Fast drilling leading to...
Losses In Subsea Kill Operations
In subsea situations, a pressure loss exists when circulating through the choke due to the friction losses in the extended choke line running up from the BOP. This pressure loss is not accounted for in normal Slow Circulating Rate SCR measurements, which are taken while circulating up the marine riser see Fig 1.19 . If the normal method of bringing pumps to kill speed is followed that is, choke manifold pressure maintained equal to SICP until kill rate is achieved , bottom hole pressure will be...
Drilling Spools
While choke and kill lines may be connected to side outlets of the blowout preventers, many operators prefer that these lines be connected to a drilling spool installed below at least one preventer capable of closing on pipe. Utilisation of the blowout preventer side outlet reduces the number of stack connections by eliminating the drilling spool and shortens the overall preventer stack height. The reasons for using a drilling spool are to localise possible erosion in the less expensive spool...
Figure NL SHAFFER SPM VALVE REGULATORS
Each subsea control pod contains two regulators - one to regulate pressure for the ram preventers and one to regulate the pressure for operating the annular preventers. Some control systems incorporate a third regulator so that the operating pressure of each annular preventer can be individually manipulated. Typical regulators are 1 l 2 hydraulically operated, stainless steel, regulating and reducing valves. As shown in Fig 9.11 the output line of each regulator is tapped and the pressure...
Kick Tolerance
When a gas influx has entered a well there are 2 critical locations for the influx - a When the influx is at the bottom of the well. In this case the SICP must not exceed the MAASP, if the formation is not fractured at the casing shoe. b When the influx has been circulated up to the casing shoe, by a constant bottom hole pressure method. In this case, the pressure at the choke must not exceed the MAASP. Formation strength, fracture pressure or fracture gradient. Formation pore pressure,...
Kick Detection And Precautions To Take While Drilling
a First indication of a kick while drilling would be an increase in flow rate. b If the increase in flow rate is not picked up then the second indication of a kick would be a pit level increase. c While drilling the horizontal section mixing chemicals or slow addition of mud into the active system should be avoided 5.9.2 KICK DETECTION AND PRECAUTIONS TO TAKE WHEN MAKING CONNECTIONS. a The equivalent circulating density is relatively higher when drilling high angle wells. While drilling, the...
Buoyancy
9.2.28 For deeper waters, it may be impractical from an operating view point to install sufficient units capable of providing adequate tensioning. In these cases, some types of riser buoyancy may be the solution flotation jackets, buoyancy tanks, etc. Buoyancy reduces the top tensioning requirements but loses some of its effectiveness as a result of the increased riser diameter exposing a greater cross sectional area to wave forces and ocean currents. Selection of the optimum method and or...
Leakoff Tests
The leak-off test establishes a practical value for the input into fracture pressure predictions and indicates the limit of the amount of pressure that can be applied to the wellbore over the next section of hole drilled. It provides the basic data needed for further fracture calculations and it also tests the effectiveness of the cement job. The test is performed by applying an incremental pressure from the surface to the closed wellbore casing system until it can be seen that fluid is being...
When To Use Volumetric Well Control
A gas kick is taken and is migrating and the drill string is plugged and only casing pressure can be read. No drill string in the well, packer leaking, wireline logging and swabbed gas migrating. Figure 5.9 Example of volumetric well control with a plugged bit TVD TVD Shoe DP csg OH cap DC OH cap Mud wt Influx Grad Casing Press 0.0459 bbl ft 0.0291 bbl ft 12.0 ppg 0.12 psi ft 700 psi Active pit volume before kick 120 bbls Active pit volume after kick 130 bbls For calculating safety margins and...
Pipe Stripping Arrangements Surface Installations Purpose
During operations on a drilling or producing well, a sequence of events may require tubing, casing, or drill pipe to be run or pulled while annular pressure is contained by blowout preventers such practice is called stripping. Stripping is normally considered an emergency procedure to maintain well control however, plans for certain drilling, completion, or well work operations may include stripping to eliminate the necessity of loading the well with fluid. Stripping techniques vary, and the...
Pipe Rams
Cameron pipe rams are available for use in Cameron ram-type BOPs to fit all commonly used sizes of tubing, drill pipe, drill collar or casing. Cameron pipe rams are self-feeding and incorporate a large reservoir of packer rubber to ensure a long-lasting seal under all conditions. Ram packers lock into place and are not dislodged by well flow All Cameron pipe rams are suitable for H2S service per NACE MR-01-75. CAMRAM top seals are standard for all Cameron pipe rams except U BOPs larger than...
The Wait And Weight Method
The Wait and Weight is sometimes referred to as the 'Engineers Method' or the 'One Circulation Method'. It does, at least in theory, kill the well in one circulation. Once the well is shut in and pressures stabilised, the shut in drill pipe pressure is used to calculate the kill mud weight. Mud of the required weight is made up in the mud pits. When ready, kill mud is pumped down the drill pipe. At commencement, enough drill pipe pressure must be held to circulate the mud, plus a reserve...
Kick Detection And Well Control Problems On Deviated And Horizontal Wells
Kick behaviour can be significantly different in highly deviated and horizontal wells. If influx is mainly gas, problems can be experienced getting the gas to move out of the horizontal section. It maybe impossible to remove the gas if the horizontal section is greater than 90 degrees. Swabbed influxes can be hard to detect in horizontal sections and care must be taken while making connections or tripping in these sections of the hole. Drill pipe pressure graphs will also be significantly...
Marine Riser Tensioning System
9.2.23 The marine riser tensioning system provides for maintaining positive tension on the marine riser to compensate for vessel movement. The system consists of the following major components a. tensioner cylinders and sheave assembly. b. hydropneumatic accumulators air pressure vessels, c. control panel and manifolding, d. high pressure air compressor units, and e. stand-by air pressure vessels. Tensioning at the top of the riser is one of the more important aspects of the riser system, as it...