Seal 9 barrier verification by xlot and Communication test P&A Forum 18 th Oktober 2017 Daniel Tomczak and Roar Flatebø
Content Valhall overview and P&A Strategy Qualifying External Barriers Coil Tubing Operation Regulations Leak Off and Communication test Field example, result Discussion Conclusion 2
Valhall DP P&A Strategy Continuous Learning and Risk Reduction Valhall DP P&A strategy: Establish barriers as deep as possible. Efficiency in P&A is contingent on simplifying operations based on learning from repeated operations Establish a track record, then apply to analogous wells/scenarios. 3
Qualifying External Barriers Dual Cemented Liner No logging tools available Rig operations complex and time consuming Pull tubing and packer Mill out inner liner (5,5 45,5 ppf heavy wall) Log Potentially perf and wash (tool size) Potentially mill second liner. Cement and test Gauge Carrier at 3035mMD, 2349mTVD Seal Assembly at 3045mMD, 2359mTVD Muleshoe 3050 mmd 7" ECP at 3152mMD (not inflated) 7" ECP at 3162mMD (not inflated) 7" Liner shoe at 3172mMD, 2483mTVD 4
Qualifying External Barriers Dual Cemented Liner What can we do with existing intervention tools? We can perforate We can set plugs We can isolate perforations We can pump cement 5
CT Seal 9 Coiled Tubing P&A Strategy Communication Testing in xlot mode Isolate reservoir with permanent bridge plug. Perforate dual cemented liners in to Seal 9 Perform xlot to verify external-most barrier to reservoir Perform communication tests in xlot between 30 m perforations up and down (3 sets minimum) Confirms liner annulus cement Confirms external-most barrier Lay cement across perforated interval and pressure test 6
CT Perforating Multiple Casings Perforated 16 zones: success every time. Perforated two zones in one run. Perforated casings: A-2, 3 zones: 5 23,2 ppf x 7 29 ppf cemented (0,89 of steel) A-19, 6 zones: 5-1/2 45,5 ppf x 7-5/8 33,7 ppf cemented (1,36 of steel) A-12, 7 zones: 5-1/2 45,7 ppf x 7 32 ppf cemented ((1,39 of steel) Repeatable xlot in every perforation at expected values. 7
Communication Testing Tested numerous CT packer tools Used Retrievable bridge plugs with memory pressure sensors under Optimized tool selection based on tool mechanics and well status (i.e. well deformations). 3 wells with access to Seal 9 External formation integrity/cement integrity confirmed in every well. Repeatable xlot in every perforation at expected values. Attempted drawdown test to induce shale influx Good liner annulus cement was found in three diverse well configurations and cement qualities Developed new strategy and tool selection process to reduce risk, scope and time for further campaigns. 8
Liner Cement and External Barrier Qualification Matrix A-2 A-19 A-12 Inner liner size 5" 23,2 ppf 5,5" 45,5 ppf 5,5" 45,5 ppf Outer Liner Size 7" 29 ppf 7-5/8" 33,7 ppf 7" 32 ppf liner ECPs yes - not inflated. no no Liner Annulus Cement Centralisation Partial none none Hole angle at shoe 8,1 deg 90,2 deg 93 deg Rotation of Pipe yes no - stuck liner yes Losses <20% 30 % 0 Top squeeze no yes no Expected annular cement GOOD BAD GOOD XLOT And Communication Tests Summary Length between Lowermost and 60 mmd 217 mmd 289 mmd uppermost perforation Bottom XLOT Communication Tests -Leak off and Breakdown pressures are corresponding to expected formation strength -The xlot show expected values regarding formation strength at the perforated depth -It is concluded that there are sealing material outside the casing and no hydraulic communication to the reservoir or permeable formations in the overburden from this perforation 3 perf intervals, all ok. Zone 1 and 2- failed comms test. Zone 2 and 3 - no communication. Zone 3 and 4 - failed comms test. Zone 4 an 5 - no communication. Zone 5 and 6 - failed comms test. -All breakdown pressures correspond to expected formation strength. -Leak off pressures in lower 5 zones indicated slight permeability. -Upper 2 perforations leak off to expected pressure (good liner cement) Zone 1 and 2- failed comms test. Zone 2 and 3 - failed comms test. Zone 3 and 4 - failed comms test. Zone 4 an 5 - failed comms test. Zone 5 and 6 - no communication. Zone 6 and 7 - no communication. Conclusions: External formation integrity/cement integrity confirmed in every well. Repeatable xlot in every perforation at expected values. Good liner annulus cement was found in three diverse well configurations and cement qualities 9
Shale as an Annular Barrier: What the regulations and guidelines say BP BP BP NORSOK 10
Shale as an Annular Barrier: What the regulations and guidelines say Two casing strings exclude logging of potential shale barrier on the outer casing Formation integrity (LOT) and communication tests are performed to qualify log responds Justification to only use LOT and communication test Perform extended LOT Testing with water Test sufficiently short intervals The test involve both the internal cement between the casings and the shale collapse on the outer casing 11
Extended Leak Off Test and Communication Test Applied pressure Perforation at 4066 Perforation at 4096 TOC 4113mMD Plug with gauge below Overview of the entire Extended Leak Off Test cycle Overview of the downhole configuration for the Communication test 12
Surface pressure (bar) xlot and coms test between 4096 and 4066 mmd Peak pressures ~240-260 bar Fall off pressures ~213 bar, expected closure pressure 13
BHP psi xlot and coms test between 4096 and 4066 mmd BHP pressure Gauge pressure below packer Formation breakdown Fracture propagation pressure Fracture closure pressure First cycle, sudden pressure increase when differential pressure is applied, followed by sudden flat platau Second cycle, sudden increase followed by dropping pressure The respond on the pressure gauge is interpreted as packer movement and not hydraulic communication due to leak 14
Overview of perforations and barrier placment and in Seal 9 15
Discussion Logs give contact length and variation in contact (length and circumferential) LOT and communication tests performed to remove uncertainty in the sealing capacity of the bonding Uncertainty removed if LOT test performed in an interval with weakest bond, sometime difficult to do as it may require testing very short intervals In the absence of logs Uncertainty regarding contact length and variation of the bond Are LOT and Communications tests of 30 m MD sufficient to qualify an interval? Fluids requirement, water, brine, mud?? Permeability responds Dependent on fluids Even ordinary LOT performed with mud show presence of permeability, how to determine acceptable levels? Length of the barrier is about adding in a safety margin and choke effect when breached? A barrier in the order of a few meters would be sufficient as long as it is tested and is holding formation strength (repeatedly) and positioned at relevant depths? However, when breached the choke effect is determined by length 16
Conclusion By doing the Extended Leak Off Tests and Communication Tests the consensus in the P&A team is that the method is sufficient to demonstrate hydraulic sealing intervals Tests are performed with water Formation Integrity is demonstrated according to expected values Tested intervals is believed to be sufficiently short By adding up the tested intervals barriers are according to regulations 17