Numerical study on debonding failure of cement plug/formation interface in open-hole temporary abandoned wells

Abstract This article presents a unique case study where operating company, Kuwait Oil Company (KOC), decided to make an attempt to perform open hole side-track through a very narrow side-track window along with other exiting conditions such as severe downhole losses and drill through very challenging formation. To deliver such project in first attempt requires very detailed planning, close coordination with various service partners such as directional drilling and cementing. Placing a good side-track cement plug in such formation was a challenge, and 2nd challenge to get kicked off from this narrow window in first attempt which was the key. In case of failure, whip stock option has to be planned as a contingency, which possess new challenging of opening a depleted zone leading to commingling low/high pressure formation which could cause a complicated problem such as borehole stability, leads to stuck pipe problem. Failure to side-track from open hole could end of planning to drill extra hole which required extra casing string to run which will put this project well over AFE and heavily impact on well objective. This open hole Side-track was planned because while drilling original hole (12 ¼" hole section) close to planned well TD, experienced complete losses. In attempt to cure the losses, LCM was pumped with no success. Performed thixotropic cement plug job for losses control. While performing thixotropic cement plug job, the cement flash set before finishing the displacement, leading to stuck string. After backing off string and fishing attempts, unable to recover the fish completely. Fish left in hole leading to only 68 ft of open hole window available to side-track where performing a cement job was impossible due to severe losses. Only way to secure the well is to try for open hole side-track. With existing sever loss situation for initiating open hole side-track was a serious challenge due to lack of side force and flow restriction to initiate the side-track. Extensive pre-job planning, peer review and risk assessment was done in coordination with various service partners to deliver such challenging side-track. A hazard analysis decision tree was established to pinpoint the risks and appropriate mitigation measures along with contingency plan put in place. A detailed side-track guidelines was shared and review with the field crew. The wellbore was successfully side-tracked through a challenging reactive shale formation in a first attempt using a customized kick-off BHA, which not only helped to avoid loss zone in side-tracked hole but also provide additional cost savings to the company. The good hole condition at the side-track point was important to enable smooth passing of the following directional BHA to achieve directional goals.

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Making Workovers Easy and Cost Effective: Turning Old Ways into New Opportunities

10.2118/206086-ms ◽

2021 ◽

Author(s):

Mustansar Raza ◽

Hossam Elmoneim ◽

Kris Looten ◽

Omar Elzanaty ◽

Ahmed Shakeel ◽

...

Keyword(s):

Gas Flow ◽

Short Interval ◽

Cost Effective ◽

No Production ◽

Wellbore Integrity ◽

Open Hole ◽

Gel Composition ◽

Cement Plug ◽

Placement Technique

Abstract A case study and methodology is presented to shed the light on the different processes followed during the placement of a non-damaging isolation barrier in a group of highly naturally-fractured and vugular gas wells. The temporary isolation aims at isolating the wellbore from the troublesome formation and allow the removal of the original completion string and install a new redesigned one. The process helped putting the wells back on production with-out the need to stimulate any of them. This helped client to reduce the overall workover cost by 40% and proved to be successful and efficient to complete the required operation in a time-efficient. The operator had 4 wells with OH sections ranging from 40-80m which were completed in the late 1990's with no production packer. To preserve wellbore integrity the completion string needed to be pulled and replaced by a string with production packer and DH gauges. Visco-Elastic Surfactant (VES) and calcium CaCO3 (carbonate) used ubiquitously in field operations were tested for optimal design to fill highly fractured OH without damaging formation. Caliper logs were not available, and the presence of natural fractures posed a challenge to calculate the actual OH volume. A system was developed to carry the CaCO3 into the wellbore in stages and slickline was employed to measure fill after each stage. Once the OH was filled with CaCO3 and well would support a fluid column coil tubing was used to place an acid-soluble cement plug in the short interval between casing shoe and end of tubing (6-9m). The paper describes the optimization process followed to tune the CaCO3 pads composition, gel composition, mixing and placement technique. The first well in the campaign required more than 10 times the theoretical volume of CaCO3 to fill the open hole with multiple settling issues at surface. It was concluded the surfactant gel was likely carrying the CaCO3 into the fractures. The procedure was modified to tie in a line of breaker solution to the well head allowing sufficient viscosity of the fluid to carry the CaCO3 from surface but immediately lose viscosity and allow the CaCO3 to settle in the open hole without being carried into the formation. Specific coil tubing procedures were employed to allow the setting of ultra-short acid soluble cement plugs (<6m). All wells were successfully isolated to allow the safe workover of the completion string and returned to production with no loss of gas flow, with-out the need to stimulate after the work over. The campaign exhibited a new method of employing existing technologies to achieve the objective in a highly challenging and relatively new oilfield of Kurdistan. The campaign also demonstrated the benefit, in terms of saving time and cost because of extensive pre-execution planning.

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Experimental and Numerical Study of the Open-Hole Tensile Strength of Carbon/Epoxy Composites

Mechanics of Composite Materials ◽

10.1023/b:mocm.0000039744.98869.0d ◽

2004 ◽

Vol 40 (4) ◽

pp. 269-278 ◽

Cited By ~ 21

Author(s):

R. M. O'Higgins ◽

G. S. Padhi ◽

M. A. McCarthy ◽

C. T. McCarthy

Keyword(s):

Tensile Strength ◽

Numerical Study ◽

Epoxy Composites ◽

Open Hole

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Temporary Isolation of a Prolific Open Hole Gas Zone using a Non-Damaging Methodology - A Multi-Well Case Study in a Field of Kurdistan N. Iraq

10.2118/202074-ms ◽

2021 ◽

Author(s):

Kristopher A Looten ◽

Mustansar Raza

Keyword(s):

Gas Flow ◽

Short Interval ◽

No Production ◽

Well Bore ◽

Gas Wells ◽

Close Collaboration ◽

Open Hole ◽

Cement Plug ◽

Formation Specific

Abstract Objectives/Scope A case study is presented detailing the methodology used to place a non-damaging temporary isolation barrier in a group of naturally fractured, prolific gas wells in a field in Kurdistan. The temporary isolation facilitated removal of the original completion string and installation of the redesign. Wells were returned to production with-out the need to stimulate proving success of the non-damaging methodology employed. Methods, Procedures, Process The operator had 4 wells with OH sections ranging from 33-181m which were completed in the 1980’s - 1990's with no production packer. In order to preserve well bore integrity the completion string needed to be pulled and replaced by a string with production packer and DH gauges. A procedure was developed to fill the highly fractured OH with a mixed particle size CaCO3 carried into the wellbore by a non-damaging surfactant based gel. Caliper logs were not available and the presence of natural fractures posed a challenge to calculating the actual OH volume. A system was developed to carry the CaCO3 into the wellbore in stages and slickline was employed to measure fill after each stage. Once the OH was filled with CaCO3 and well would support a fluid column coil tubing was used to place an acid soluble cement plug in the short interval between casing shoe and end of tubing (8-10m) Results, Observations, Conclusions The first well in the campaign required more than 10 times the theoretical volume of CaCO3 to fill the open hole. It was concluded the surfactant gel was likely carrying the CaCO3 into the fractures. The procedure was modified to tie in a line of breaker solution to the well head allowing sufficient viscosity of the fluid to carry the CaCO3 from surface but immediately lose viscosity and allow the CaCO3 to settle in the wellbore without being carried into the formation. Specific coil tubing procedures were employed to allow the setting of ultra-short acid soluble cement plugs (<10m). All wells were successfully isolated to allow the safe workover of the completion string and returned to production with no loss of gas flow, with-out the need to stimulate after the work over. Novel/Additive Information The campaign exhibited a new method of employing existing technologies to achieve the objective in a highly challenging and relatively new oilfield of Kurdistan. The campaign also demonstrated the benefit of the operator and service company closely collaborating on each step of a novel process. The workovers would not have been successful with-out the close collaboration of the two companies.

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