Abstract

Historically, coiled tubing (CT) services were positioned as highly tailored services in Russian Federation. Main operations for CT application were post-frac cleanouts (CO) and kick-off (KO) of vertical and slightly deviated wells. Lately, with increasing of horizontal wells quantity, CT application scope became wider: logging, perforating, fishing jobs, CO, milling and other operations. With increasing interest to multi-stage hydraulic fracturing technology, Coiled Tubing application has to grow to meet client demands. In wells with horizontal section 1000 m long, milling of different sizes balls and seats became the most challenging and efficient technical solution.

Located in Khanty-Mansiysk District of Western Siberia, Priobskoe field is one of the world’s largest oilfields. Due to low permeability almost 80% of reserves are hardly recoverable. Oilfield development plan include post drill fracturing of all new completed wells. In order to maximize the hydrocarbon recovery field-proven technology enabling multi-stage hydraulic fracturing of an uncemented completion in one pumping treatment became a consistent decision for well treatment.

For the first job following workflow was applied: multi-stage hydraulic fracturing completion was installed and 7 zones were fractured one by one. Technology implies that during pumping, at specified stage time, balls are dropped (one at time) from the surface to open the Frac Ports (FP). After the treatment, the most efficient technical solution to remove the balls is to mill them using CT. Following milling operations the well was cleaned out and kicked off with nitrogen. In designing a Coiled Tubing job the critical part is BHA and string selection. Selected mill should be strong enough for milling Frac Port iron and long enough to prevent damage of FP, by side tracking from it to reservoir.

As per project program 4 wells have been completed with technology described above. Current production rates show high efficiency of multi-stage hydraulic fracturing technology over traditional well completions. This article describes technical and operational details of the project, candidate selection process, job planning and determines a way to find an optimum technique to meet client demands. Analysis of 4 wells completed with multi-stage fracturing liner is shown in comparison with standard completion in the article.

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