1. Fluid in Hole
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Primary pressure control while drilling and working over will be fluid gradients.The drilling program must detail the appropriate mud gradient required for drilling under normal static conditions (based on best knowledge or prediction of formation pressures as detailed in the well prognosis provided by PDD).
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Conventional drilling, completion and workover activities must be carried out with hole full of drilling fluid of appropriate density to prevent any influx of formation fluids.•
When drilling from 0-4000 ft, the mud must provide a 50 to 100psi overbalance at the expected top of any potentially productive formation.•
When drilling hydrocarbon bearing zones below 4000 ft, the mud must provide an overbalance of 250 – 300 psi (exceptions to be approved by HDO) with appropriate risk assessment.•
After determining the formation shoe bond strength at the shoe of each casing string, the well control plan for that hole section must be agreed in the light of the information available. Refer to table (1-3)•
During workover (cased hole) operations, brines must give 300 psi overbalance at top perforations. Refer to table (1-3)•
Completion fluids must be 2 pcf higher than the mud used for drilling the horizontal hole or the zone to be perforated.1.1 Losses
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When drilling hydrocarbon zones or with hydrocarbon zones exposed under partial loss conditions, the mud weight will be based on a balance between reducing the losses to a manageable level, and preventing kicks. Non damaging plug must be spotted to maintain the required overbalance prior to continue drilling.o A minimum of one and half hole volume must be kept in the tanks for emergency.
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30 Tons (metric) of LCM must be stored on site at all times to allow•
Water supply requirements are dependent on lost circulation problems.Under normal circumstances the water supply must not drop below 100 bbls/hr. For exploration wells, a minimum of 150 bbls/hr must be available.
1.2 Leak-off Test
Leak-off test must be carried out in exploration wells only or when requested by PDD and included in the well program.
1.3 Shoe Bond Testing
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Shoe bond test will be performed in all wells after drilling out 10 ft of new formation (except for conductors, 18 5/8” surface casing and horizontal holes). Corrective measures will be performed if the open hole pressure integrity fails.Table 1-3: Surface pressures for shoe bond testing
Casing/Formation Approximate
Deep Conductor 400 Not required
18 5/8” Casing @ Dammam 1600 Not required
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Shoe Bond test must be conducted after displacing hole to the new drilling mud for drilling the new hole section.•
Refer to Volume-2, Chapter-3 “Special Well Operations” for shoe bond test procedures.1.4 Flow Checks
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Flow checks while drilling must be made if a gain or loss of 5 bbls is detected.•
Flow checks must be performed whilst tripping out of hole:o When pulling off bottom.
o After pulling into the casing shoe.
o Every 3000 ft inside casing.
o Before the BHA enters the BOP stack.
1.5 Tripping
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Where hole is drilled across a pay zone, the Drilling Supervisor must be on the rig floor prior to each trip.•
Circulation of a minimum of one bottom up (twice bottom up for horizontal holes) or until hole clean is required.•
Flow check the well and then observe a minimum of 10 stands pulled off bottom, or until such time as the DS is satisfied that the hole fill volume is correct according to the trip sheet.•
No trip is to be made if the static loss is more than 20 bbls per hour. The hole is to remain full throughout the trip with the trip sheet monitored closely. All effort to be made to minimize losses before tripping out.•
After completing all well kills after well testing operations a minimum of one complete hole circulation is to be performed prior to pulling out of the hole.•
In open hole pipe tripping speed must be limited to one stand per 30 seconds to avoid swabbing or surging the hole.•
When an influx of formation fluid into the well bore is detected the well must be shut in immediately using the Hard Shut In Method using the annular BOP first.•
Special tripping practices for sour gas wells must be made prior to POOH, this includes short trip of 5 stands to ensure hole is not swapped. A pill of scavenger must be spot on bottom.1.5.1 Trip Sheets
Trip sheets must be filled out by the driller on every trip in and out of the hole every 5 stands of DP’s and every 2 stands for DC’s.
1.6 Slow Pump Rate (SPR)
Two Slow Pump Rate at 30 SPM and 45 SPM for each pump must be taken at least:
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Start of tour•
At a bit or BHA change•
Every 500 ft.•
When the mud weight is changedPressure must be recorded using the same gauge to be used for killing operations.
1.7 Equipment and Mud Materials
The following kick detection / equipment / instrument is the minimum required to be operational on Categories (A) High Risk Wells and (B) Medium Risk Wells.