The Evolution of Completion Practices and Reservoir Stimulation Techniques in the North Sea

Bocaneala, Bogdan; Barrett, Charles; Holland, Brian; Langford, Marc; McIntosh, K. D.; Nitters, Gerrit; Norris, Mark Robert; Orski, Karine

doi:10.2118/175443-ms

All Days 2015

DOI: 10.2118/175443-ms

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The Evolution of Completion Practices and Reservoir Stimulation Techniques in the North Sea

Bogdan Bocaneala

Charles Barrett²,

Brian Holland

et al.

Abstract: The objective of this paper is to collate and share with the industry the technical knowledge on hydraulic fracturing and related completion practices accumulated from both operating and service companies throughout the North Sea. We will follow the evolution of completion technologies and hydraulic fracturing techniques from the early 1980s, when hydraulic fracturing offshore was in its infancy, to present-day modern practices. Although the North Sea hydrocarbon production has been in decline f… Show more

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Cited by 4 publications

References 11 publications

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World's Deepest Single-Trip Multistage Fracturing through 2-7/8-in. 7,400-m Coiled Tubing String: Method Development and Learnings from Norway

Keong¹,

Jaimes²,

Mussenov³

et al. 2023

Day 2 Wed, March 22, 2023

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The Valhall and Hod chalk fields have seen the rise of single-trip multistage fracturing (STMF) that allows stimulating two to four zones in a single day in contrast to the average of one zone every 2 to 3 days for conventional applications. Recent advancements focus on lowering operational costs while bringing wells on production faster. One way of doing this is to further improve the STMF method by the introduction of fracturing through coiled tubing (FTCT). Conventional multistage fracturing operations use the plug-and-perforation method to complete each stage separately. With a sliding sleeve completion, coiled tubing (CT) is used to manipulate sleeves; then, proppants are pumped down the wellbore without CT in the well. Conversely, STMF uses a bottomhole assembly (BHA) with sleeve shifting tool and multiset packer for selective proppant stimulation down the CT-tubing annulus. Any underflush of proppants is cleaned by CT forward circulation. FTCT builds upon the STMF method, but proppants are pumped through CT. The underflush proppants are reverse circulated out of CT through a BHA without a check valve. FTCT was first used in a well at 5,000-m measured depth (MD) using a 6,700-m 2 7/8-in. CT. Data from this operation were used to match the friction calculation. In the second well at 6,500-m MD, intervened with a 7,400-m-long CT, 10 zones were stimulated using FTCT, and 2 zones with conventional fracturing. FTCT only required 8.5 hours whereas conventional fracturing took 75.6 hours per zone. The underflush volume was 50% less and removed through reverse cleanout that is 4 hours faster per stage compared to STMF. In the third well at 6,700-m MD, the well was killed with 1.35-SG heavy brine due to a leak in the completion. Proppant was pumped through CT and displaced with 1.04-SG brine. An increase in pumping pressure during reverse cleanout, compounded with the difference of fluid density, led to the collapse of CT section above the BHA. The collapse created difficulties for the BHA to unset, thus creating a mechanical sticking point, and hindered the ball drop release mechanism for the BHA. Awareness of pressure limitations of CT at the thinnest section is essential to improve the reverse cleanout design since high initial forces are required to reverse circulate. FTCT requires careful pressure analysis, especially when attempting operations in deep horizontal wells. Most standard CT cleanout simulation software lacks complete hydraulic modeling capabilities for reverse cleanout of crosslinked fluids with proppants. Data gathered from the three operations are thus important to improve the method. This study highlights associated challenges, considerations during design, operational benchmarks, and learnings from the world's longest FTCT operation in the North Sea.

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World's Deepest Single-Trip Multistage Fracturing through 2-7/8-in. 7,400-m Coiled Tubing String: Method Development and Learnings from Norway

Keong¹,

Jaimes²,

Mussenov³

et al. 2023

Day 2 Wed, March 22, 2023

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Successful Execution of Hydraulic Fracturing via a Multi-Stage Ball Drop Completion to Extend Platform Life and Access Previously Untouched Reserves in a Challenging Operational Environment – A Central North Sea Case Study

Channa,

Bocaneala,

Wood

et al. 2023

Day 3 Thu, September 14, 2023

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In 2019 the Armada hub was evaluated for drillable targets to exploit previously untouched reserves and extend the life of the platform. Seymour Horst oilfield, the most eastern of fields served by Armada, was discovered in 1983, and appraised the same year. These wells were drill stem tested in multiple zones, but all had low production rates. Reservoir simulation work estimated that drilling and completing a long horizontal well in Seymour Horst's upper and middle Skagerrak sands followed by multi-stage hydraulic fracturing treatments to overcome reservoir compartmentalization and low vertical permeability would bring the well to economic rates. Well 22/5b-A14 was sanctioned and drilled in 2019/2020. Execution of hydraulic fracturing campaigns in long horizontal wells in the challenging North Sea environment is complex, with great emphasis on operations efficiency. Considerable time was put towards each element of the well construction and job design, including the modelling of reservoir characteristics critical for fracturing, multi-stage fracturing completion design, fracturing materials, management of resources onsite during execution, and the design of the CT string to be used as contingency. This paper describes the detailed planning process and utilization of a combination of new North Sea technologies and operational techniques to successfully execute the campaign with large proppant volumes in the high temperature reservoir, in a challenging offshore environment, in an efficient and cost effective manner. Over 40,000 Bbl. of clean fluid and 2,500,000 lbs of 16/20 resin coated ceramic proppant with ~7.5% of that volume being infused with scale inhibitor, was pumped into the well from the dedicated stimulation vessel. The campaign was executed over the winter months in 2020, and therefore was subjected to waiting on weather delays. As a result, the vessel operating efficiency was 11% vs the estimated 22%. However, the use of the ball actuated multi-stage system eliminated five of the seven intervention operations that would have been required in a conventional completion system between each stage, saving valuable rig time, and allowing the stimulation vessel to maximise the use of the operable weather windows. Further time savings were made through use of water bunkering operations, reducing the number of sailings required by the stimulation vessel to place such a large volume of fluid and proppant. Production rates, while initially lower than expected, remain sustained. There have been no issues with scale to this date.

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Case History: Application of a Novel Workflow to De-Risk, Plan and Execute Efficiently a Drill to Frac Project in North Sea

Mocanu,

Bocaneala,

Norris

et al. 2023

Day 1 Tue, September 12, 2023

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The Southern Sector of the North Sea comprises numerous gas sandstone reservoirs typically exploited by dry tree steel jacketed platforms of 2 - 20 wells. This paper describes in detail the case history of a successfully planned, drilled and hydraulically fractured new well targeting Leman sandstone within an extensive field located 150 km off the UK coast. The objective was to drill a well in a largely unexploited part of the reservoir and use fracturing as a commercial completion in the low permeability Fault Block 1. Due to the unknown and varying characteristics of the underlaying Westoe Formation with sandstones potentially extending into the water leg, and thus providing a conduit for water, coupled with a challenging environment, an efficient team collaboration was of critical importance for the best outcome of the project. Risks related to hydraulic fracturing operations were extensively explored in the early phase of the project through a detailed study and assessment of the uncertainties impacting the final results. One of the key uncertainties was reservoir proximity to water and associated risk of fracture connection. The target reservoir block is bound by the presence of a fault on the north which imposes additional operational risks. A study using a new and novel uncertainty driven frac design workflow was carried out prior the drilling phase to identify, highlight and quantify the key uncertainty factors with associated risks related to proppant fracturing technical aspects as well as their potential impact on the fracturing outcomes. This allowed technical and operational risks to be effectively managed throughout the project. Expertise of the applicable disciplines were captured through a close collaborative approach coupled with the use of an innovative consensus tool. During the hydraulic fracturing operations, a suite of diagnostic tests was performed followed by three temperature log runs allowing the hydraulic fracture height to be de-risked. Naturally this provided additional inputs for fracturing model calibration and final fracture design adjustments. The well was successfully drilled and completed with a single proppant fracture from a vertical wellbore through the primary reservoir horizons. The resulting production, with a low BS&W, was in line with the planning projections and forms a detailed and validated dataset for the consideration of future vertical single, or multiple fractured horizontal wells in the field. This project has proven the feasibility of new area development and effectiveness of correctly applied fracturing workflows and techniques in this and other fields in the area. A novel uncertainty driven frac design workflow was applied at an early planning phase to identify and quantify the key uncertainty factors with associated risks related to proppant fracturing technical aspects as well as their potential impact on the fracturing outcomes. Applicable disciplines and their expertise were captured through a close collaborative approach coupled with the use of an innovative consensus tool to expedite the drive to an optimum solution.

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The Evolution of Completion Practices and Reservoir Stimulation Techniques in the North Sea

Cited by 4 publications

References 11 publications

World's Deepest Single-Trip Multistage Fracturing through 2-7/8-in. 7,400-m Coiled Tubing String: Method Development and Learnings from Norway

World's Deepest Single-Trip Multistage Fracturing through 2-7/8-in. 7,400-m Coiled Tubing String: Method Development and Learnings from Norway

Successful Execution of Hydraulic Fracturing via a Multi-Stage Ball Drop Completion to Extend Platform Life and Access Previously Untouched Reserves in a Challenging Operational Environment – A Central North Sea Case Study

Case History: Application of a Novel Workflow to De-Risk, Plan and Execute Efficiently a Drill to Frac Project in North Sea

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