Packing Unit Replacement Screwed Head
The following steps are required to remove the packing unit. 7 Clean and lubricate BOP head and body threads 8 Replace head and tighten to align for lock screw 9 Install lock screw and torque to 100 ft lbs
Gas Migration
If a gas kick enters a well, the pressure of gas at that point is formation pressure PF , ignoring any skin damage effects . Gases are compressible and thus store energy for later release. Considerable energy can be stored in this way. Liquids, in contrast, are virtually incompressible, and because little or no change in volume occurs little energy can be stored. This characteristic of gas means that when a well is shut in with a gas kick, the gas in the well retains the prevailing pressure at...
Well Control From A Floating Rig
Well Control on a floating rig can present special problems that are not encountered on land or fixed bottom rigs. These problems can be summarised as follows. Kick Detection can be more difficult due to the motion of the vessel. Mud surges in a flow line or fluid movement in mud pits can make the detection of small inflows into the well very difficult to detect. Fracture Gradients. Fracture gradients are a function of overburden and formation fluid pressures. As water depth increases the...
Diverter Procedure While Drilling
1 When a possible indication is observed, STOP the rotary, pick up until spaced out. 2 Shut down pumps and check for flow. If positive 3 OPEN diverter line valves- check that flow will be diverted to downwind side of rig. 5 CLOSE diverter annular BOP. 6 Start pumps ideally to pump water at maximum possible rate, for lubrication. NOTE On many rigs, there is a mechanical interconnection to prevent the diverter annular closing, until the diverter line valves are opened. This is to prevent an...
Constant Bhp Kill Methods
There are three 'constant bottom-hole pressure' kill methods in common use today which are Wait amp Weight Method also known as the 'Engineer's Method' These three techniques are very similar in principle, and differ only in respect of when kill mud is pumped down. In the Driller's method, the kill is split into two circulations. During the first, the kick fluid is circulated without changing the mud weight once the kick is out, the mud is weighted up and pumped around the well on the second...
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...
Soft Shutin Procedure While Tripping Fixed Rig
1 When a possible sign is observed, set top tool joint in the slips. 2 Install a full opening Safety valve on the drill pipe. Close the valve once it is installed. 3 Pick pipe up, check for flow. Check trip volumes. 4 OPEN choke line valve at Bop stack. HCR valve . 6 CLOSE choke. If this is not a positive shut-off type, it is necessary to close a valve just downstream of the choke in order to read well pressures. 8 Stab IBOP Grey Valve and open full opening safety valve. 9 Read and record...
Umbilical Hose
The umbilical transmits all power fluid and all pilot signals from the surface to the subsea control pods. Hydraulic pressure from the regulated side of the subsea regulators is also transmitted through the umbilical to pressure readback gauges at surface. The power fluid is supplied only to the umbilical of the selected active pod, whereas pilot pressure is normally supplied to both the active and inactive pods. Figure 63 Hose Reel Control Manifold Figure 63 Hose Reel Control Manifold rilling...
Drill Pipe 1
Figure 5 shows that the adjustable choke has been OPENED and exactly one barrel of mud, including leakage past the BOP, has been bled. a Pressure in the gas sand 5400 psi b Bottomhole pressure 5400 psi c Surface pressure 450 psi Note that the wellbore pressure has returned to the original value Figure 3 . By bleeding one barrel of mud, the gas bubble expanded back to its original volume and the wellbore pressure dropped 50 psi. From this, the following conclusions can be made 1 If mud is bled...
Low Choke Method
After observing the maximum allowable surface pressure, choke adjustment may be made to hold the casing pressure constant. This will steadily reduce BHP. This procedure is to be limited at most to a 150 psi drop in BHP. The effect of annular friction loss acts as a small safety margin before influx occurs. In many cases this procedure allows time for the influx to be circulated past the casing shoe before a further significant influx occurs. This depends, amongst other things, on formation...
RIGTRAllM Uxv
See Figure 2. A Floating Rig in 900 ft. of water, with the same shoe depth and fracture gradient, the 12 ppg mud would give a maximum surface choke pressure of 624 psi. See Figure 3 In 2.970 ft of water, with the same shoe depth and fracture gradient. It would not be possible to circulate 12 ppg mud without losses. A 12 ppg mud would give zero tolerance, as it almost equals the pressure required to fracture the formations.
Rams Subsea
Besides sealing off the annulus, the pipe rams are able to support the weight of the drill string up to some 600,000 lbs if it needs to be hung off on them killing operations or during periods of bad weather. To do this safely, the rams must be able to be locked in the closed position. Cameron U-type preventers use a wedge lock device. This is a tapered wedge, hydraulically operated, which moves behind the tail rod of the ram operating piston thus holding the ram firmly closed. The wedge can...
Mud Salinity
Specific mud characteristics measured in the suction pit are compared with measurements after circulation. Mud resistivity, chloride ion content, pH variations, and other specific ions are closely monitored. Gains or losses of specific ions are correlated to down-hole pressure differentials by proprietary logging methods Delta Chloride Log and used in predicting mud weight requirements. Invasion of the drilling mud by formation water can sometimes be detected by changes in the average density...
Well Data
Frac. Gradient Breakdown pressure at shoe DC OH Capacity DP OH Capacity MAASP Assume SIDPP Influx gas Formation pressure 0.0291 bbls ft 800 ft Collars 0.0459 bbls ft 0.72 - 0.52 x 5000 ft 1000 psi 500 psi 0.12 psi ft 500 10000 ft x 10 x 0.052 5700 psi 1250 ft This will cover the collars and 450 ft of pipe. Collars 23.28 bbls Around the pipe 450 ft x 0.0459 20.655 bbls Total length 1250 ft Total volume 43.935 bbls Step B 1250 ft converted to a volume below the shoe. 1250 x 0.0459 57.375 bbls...
RIGTRAllM Gxt
Kick Tolerance. Is the maximum kick volume that can be taken into the well and circulated without the causing formation damage. Kick tolerance is a function formation pressure and formation breakdown pressure. Increased water depths and the inclusion of riser margins reduce kick tolerance. Choke Line Friction Losses. CLFL Is the pressure losses created when circulating through a choke line. On a floating rig, kicks will be circulated to surface through the choke line. It is therefore important...
CONTENTS Sww
1.1 AUXILIARY WELL CONTROL EQUIPMENT 3 1.4 STRIPPING OPERATIONS 39 1.5 ANNULARS CAMERON 'DL' 40 1.6 ANNULARS - HYDRIL 'GK' 43 1.7 PACKING UNIT REPLACEMENT - SCREWED HEAD 45 1.8 SPLITTING PACKING UNITS 46 1.9 ANNULARS - HYDRIL 'GL' PREVENTER 47 1.10 HYDRIL PACKING UNITS SELECTION 50 1.12 MUD GAS SEPARATOR POOR BOY DEGASSER 57 1.13 FLANGED AND RING GASKETS 60 1.14 HYDRAULIC BOP CLOSING UNIT 67 1.16 SUBSEA BOP CONTROL SYSTEMS 72 1.18 FAIL SAFE VALVES SUBSEA 106 1.19 SUBSEA ANNULAR HOOK-UPS 108...
Secondary Well Control Hmud Pf
If for any reason the effective head in the wellbore should fall below formation pressure, an influx of formation fluid kick into the wellbore would occur. If this situation occurs the Blowout Preventers BOPs must be closed as quickly as possible to prevent or reduce the loss of mud from the well. The purpose of Secondary Well Control is to rectify the situation by either a allowing the invading fluid to vent harmlessly at the surface, or b closing the well in. i.e. providing a surface pressure...
Sediment Compression See Figure
In areas where rapid deposition has given rise to shale bodies, sur-pressures develop as a result of compression. This is particularly prevalent in the basins where much of the offshore drilling is taking place. However, evidence of compression may be found in almost any area. When shale bodies are deposited, porosity of the clay shale is more than 50 . As deposition continues, clays compact under the weight of material above. As porosity decreases, the expelled waters find their way out...
Oil And Gas Rock Accumulations
Four common types of trap in which oil and gas may be found are shown See Figure 2. Theses are Salt Dome or Piercement Trap Figure 2 - Typical Oil and Gas Rock Formations Figure 2 - Typical Oil and Gas Rock Formations
Regan Fast ShutOff Couplings
If a kick is taken whilst the Kelly is removed from the drill string, flow up the pipe might be so strong that it is impossible to stab a safety valve. In this case, a fast shut-off coupling See Figure 69 which is designed to be dropped over the drill pipe and automatically latch under the tool joint can be used. The coupling is very heavy to assist in stabbing and has a Kelly cock either integral with it or screwed on top of it. It should be ensured that any drill pipe that might be used has...
RIGTRAllM Mov
If this start up procedure is used on a floating rig with significant choke line friction losses, bottom hole pressure would increase by a pressure equal to the friction losses. This overpressure could cause damage to the formation. There are two methods that can be implemented to compensate for this over pressure choke line friction losses . As the pump is being brought up to kill speed, the casing pressure is being reduced by an amount equal to the choke line friction losses. With the pump at...
Hangoff Procedures During Bad Weather
Whilst 'Waiting on Weather' it might be necessary to hang the drill string off from the wellhead or BOPs. In severe cases, it might also be necessary to disconnect the riser from the BOP stack. The decision to 'hang-off should be taken to allow sufficient time for the bit to be pulled safely into the casing shoe. A natural tendency for the driller to pull up too quickly could perhaps induce swabbing and a possible kick situation later. The preferred method to hang-off the string is to use a...
Casing Seat Selection
Selecting casing setting depths for each casing string to be run in a well is often the most critical decision made in pre-planning especially where abnormal pressures or weak, lost circulation zones, are expected. The key to satisfactory casing seat selection is the assessment of pore pressure formation fluid pressures and fracture pressures throughout the well. Evidently, as the pore pressure in a formation being drilled approaches the fracture pressure at the last casing seat then a further...
Hard Shutin Procedure While Drilling Fixed Rig
1 When any indication is observed while drilling that the well maybe flowing, stop rotating the drill string, raise the drill with pumps on until spaced out. 2 Stop pumping and check for flow, if positive 3 Close annular or pipe rams. 5 Call supervisor and commence plotting a graph of shut in drill pipe pressure. Check pit volume again. 6 Refer to API RP 53 for advantages and disadvantages of the hard shut-in. NOTE Choke in closed position while drilling. In any shut-in procedure it is prudent...
Heaving Shales
Excessive volumes of shale cuttings on the shaker may be an indication of an underbalanced condition. Shale is usually very porous, but has little or no permeability. Fluids in the pores are subjected to formation pressure, but are not able to flow. However, if a differential pressure exists from the formation to the well bore, such as in the case of abnormal pressure, the fluid pressure causes weakening of the walls of the hole and spalling or heaving of shale into the hole. At the surface an...
bRam to Ram Stripping
The following general guidelines apply to all pipe ram preventer to pipe ram preventer stripping. i The same general techniques are applied in ram to ram stripping as outlined in annular to ram stripping. ii When stripping with ram preventers, the lower the closing pressure, the longer the life of the sealing element. iii The pipe ram above the drilling spool should be used as the primary stripping preventer. iv The pipe ram immediately below the drilling spool should only be used to strip...
Hose Reels
The hose bundles are mounted on heavy duty reels for storage and handling and are connected to the hydraulic control manifold by jumper hoses. The reels are driven by reversible air motors and include a disc brake system to stop the reel in forward or reverse rotation. When the subsea control pod is run or retrieved, the junction box for the jumper hose is disconnected from the hose reel. However in order to keep selected functions 'live' during running or retrieval operations, five or six...
Formation Fracture Pressure Pfb
Formation fracture pressure, or formation breakdown pressure is the pressure required to rupture a formation, so that whole mud can flow into it. The symbol PFB is usually used to denote this pressure See Figure 10. Commonly this is expressed as a pressure gradient, GFB, with the units of psi foot. The formation breakdown pressure is usually determined for formations just below a casing shoe by means of a leak-off test. This test of the formation strength, also known as a formation integrity...
Differential Fluid Pressure
The classic example of a differential fluid column is the Artesian Well. Here an aquifer, or water bearing permeable layer outcrops in the hills. The drive pressure from such a reservoir equals the fluid head at any point See Figure 5. Drilling into the aquifer out on the plains, as shown in the diagram, only a relatively short column of well fluid is available to balance a big column of formation water. Hence an abnormally high pressure gradient has to be held if the well is not to blow out....
PreSpud Pressure Estimation
Determination of pore pressure formation fluid pressure is estimated by a number of methods. These methods rely on establishing the 'Normal Trend' of measured shale properties with depth and subsequently identifying any departures from the normal trend which could indicate 'Overpressure Zones'. Each method used is based on shale compaction which is, briefly, described as follows In a sedimentary basin the continuous deposit of muds and silts causes a build up of material which squeezes or...
Riser Collapse
In water depths over 1500 ft riser collapses can be a potential problem when a shallow gas kick is being diverted and all fluid is evacuated from the riser. The collapse resistance of the riser may be reduced by the considerable bending loads applied to the riser due to tension, weight and current forces. If this problem is considered a possibility, then a riser joint fitted with a special differential fill-up valve can be used. This valve automatically senses the loss of hydrostatic pressure...
Insufficient Mud Weight
The hydrostatic pressure exerted by the column of mud in the hole is the primary means of preventing kicks. Insufficient mud weight can result from penetration of an unexpected, abnormally high-pressure zone, or be due to deliberate underbalance drilling methods in field development wells. Accidental dilution of the mud with make-up water, in the surface tanks, is a relatively common occurrence, and must be guarded against. With water base muds and fast drilling, it is common to add...
Diverter Procedure While Drilling Fixed Rig
1 Where shallow casing strings or conductor pipe are set, fracture gradients will be low. It may be impossible to close the BOP on a shallow gas kick without breaking down the formation at the shoe. If a shallow gas kick is taken while drilling top hole then the kick should be diverted. Drilling shallow sand too fast can result in large volumes of gas cut mud in the annulus and cause the well to flow, also fast drilling can load up the annulus increasing the mud density leading to lost...
Graph showing change in bottom hole pressure corresponding to surface drilling
If very fast penetration is made in a gas-bearing formation, the percentage of gas in the mud is likewise increased and problems may result. The rapid expansion of gas near the surface may cause 'belching' at the bell nipple with a loss of mud from the well and a consequent drop in the hydrostatic pressure. This may induce further 'belching' and lowering of the hydrostatic pressure. This may induce further 'belching' and lowering of the hydrostatic pressure to below that of the formation so...
Flow Rate Increase
When an influx is flowing into a well with normal circulation in progress, the total volume of material flowing out of the well increases. A flow sensor, such as a flow paddle system, provides a means for measuring quite small variations in flow See Figure 1 When a kick is occurring from relatively low permeability formations, as a slow 'bleed in', it is unlikely that any variation in flow rate will be observable. Roll, and more particularly, heave on a floating vessel will provide considerable...
Incorrect Hole Fill Volume
The importance of ensuring that the correct amount of mud is added to the hole to replace the drillstring as it is removed has already been discussed. Equally it is important to ensure that the correct amount of mud returns from the hole as the drillstring is run back. Careful monitoring of trip tank volumes, or hole fill up volumes, is essential. If serious doubt exists over a discrepancy, and re-calculation and level checks still show that a discrepancy may exist, the safest response is to...
Kick Tolerance Fixed Rig Simple Method
a Maximum kick length, or Volume at shut-in MAASP - SIDPP - Mud gradient - Influx gradient Length of influx at shut-in. now, Convert to a volume in barrels. b Convert the length calculated in a above into the volume at the annulus section below the casing shoe. Volume in barrels. c Use Boyles gas law to convert this to a volume in downhole conditions. Where P1 Formation breakdown pressure at shoe. V1 Volume calculated in b .
Drilling Break
A sudden increase in rate of penetration is usually caused by a change in formation type. It may however signal an increase in permeability and a loss of pressure overbalance. Both these effects result in faster drilling. The drilling break may be spectacular, though most commonly a gradual change is seen. It is rare for the drilling break to indicate a kick is in progress, though it is often a sign that conditions are changing and formation pressure rising, which may lead to a kick.
Hard Shutin Procedure Floating Rig
1 When any indication is observed while drilling that the well maybe flowing, stop rotating the 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 again. 6 If rams have been closed then reduce manifold pressure, slack off on drill string...
Shale DensityCuttings
The examination of shale cuttings and or cores can provide information on formation pressures. Properties of shale such as bulk density, shale type, size, and shape can be related to abnormal pressures. Several techniques, such as the graduated density column method or the mud balance method, are available to measure the density of shale cuttings recovered at the shaker. Care must be exercised to separate bottom cuttings from upper hole cavings. Also, cuttings must be properly washed and or...
Total Displacement Of Drill Pipe
1 Includes tool joints, wall thickness, and internal capacity.
Using Riser PSCR vs Choke Line PSCR for Well Kill Calculations
Many people who work through Subsea Well Control calculation for the first time, often ask why the slow circulating pressure SCR through the riser is used, when the well is circulated through the choke line, and choke line slow circulating pressures is not included The following calculations are with the choke line friction losses included, this will show that the wellbore is going to be over pressurised by this choke line friction value. So adjustments must be made To enable the friction to be...
Ram Bops
Ram type BOPs are the most common type of blow out preventers. This section looks at three common types in use Shaffer 'SL', Cameron 'U' and Hydril 'V'. API RP53 requirements state that surface rams must close within 30 seconds. Subsea rams must close within 45 seconds. The Cameron 'U' BOP is a ram type preventer designed for both land and subsea operations. U BOP rams are pressure energising. Wellbore pressure acts on the ram to increase the sealing force and to maintain the seal in the event...
Pit Volume Increase
Any invasion of formation fluid must result in the expulsion of mud from the well, and this shows up as an increase in surface volume in what is, normally a closed circulating system. As is the case with flowrate, a gain in pit level may be hard, or impossible, to detect when a slow bleed-in of fluid occurs. It is also very easy for other factors to mask a change in pit level. Surface additions to the mud system, or surface withdrawals and dumpings, must be done with the Driller's knowledge....
Example Well Kill Calculation
This example is based upon the following situation Company policy is to keep the choke and kill lines full of seawater to avoid settling. A kick is taken and the well is correctly shut in and the pressures recorded. There is no Float in the string. The choke line pressure drop is known to be as follows with 13.0 ppg mud . 3.5 bbl min 450 psi The recorded slow circulating rates down the pipe and up the riser are 3.5 bbl min 800 psi
Annulars Hydril Gl Preventer
The 'GL' preventers are designed for both subsea and surface operations. Features of the 'GL' make it particularly useful for subsea and deepwater drilling. Secondary Chamber Balancing Chamber Figure 30 Hydril 'GL' Annular Preventer Secondary Chamber Balancing Chamber k Cutaway View of 'GL' BOP shown in Midstroke. 5,000 or 10,000 psi bottom connections are available in hib, API flanged, or studded connection. Figure 30 Hydril 'GL' Annular Preventer THE SECONDARY CHAMBER, which is unique to the...
Formation Fluid Pressure Pf
The formation fluid pressure, or pore pressure, is the pressure exerted by the fluids within the formations being drilled. The sedimentary rocks, which are of primary importance in the search for, and development of oilfields, contain fluid due to their mode of formation. Most sedimentary rocks are formed as accumulations of rock debris or organic material, underwater. Since over two thirds of the earth's surface is covered with oceans, the vast majority of sedimentary rocks are laid down as...
Annular Preventers
API RP53 state that surface annular preventers closing times should not exceed 30 seconds for smaller than 18 3 4 and 45 seconds for 18 3 4 and larger. Subsea annular preveters should not exceed 60 seconds. Shaffer annular BOPs are rugged, compact and will seal on almost any shape or size- Kelly's, drill pipes, tool joints, drill collars, casing or wireline. They also provide positive pressure control for stripping drill pipe into and out of the hole. The annular BOP is one of the first lines...
Bottom Hole Pressure
The term 'bottom hole pressure', as used here, means the sum total of all pressures being exerted on a well by our operations. Bottom hole pressure is the sum of the hydrostatic pressures exerted by the fluids in the well, plus any circulating friction loss e.g. Annular Pressure Loss , plus any surface applied back pressures, where appropriate. This is the total pressure exerted by us. It is usually intended to at least balance the formation fluid pressures in the exposed portion of the well.
Auxiliary Well Control Equipment
The Gray inside BOP is a heavy-duty drop check valve with a conical plug to reduce the cutting action of the mud on the valve seat, ensuring positive closure whenever required. Installed in the drill string, it protects the rotary swivel, rotary hose, standpipe, and mud pumps from drill pipe kicks. It may be used along with high-pressure pumps to maintain well control by preventing high-pressure backflow. A special release tool allows the valve to be held open to permit stabbing into position...