Verkhnechonskoe oil field is situated in Eastern Siberia, Russia. This field is quite unique due to low formation temperaturesthe bottom hole static temperature does not exceed 13 degC. This low temperature environment together with low formation fracture gradient present unique challenges for cementing operation. Conventional lightweight system extended by sodium silicate does not meet client well acceptance criteria -no sustained casing pressure (SCP) and successful annular space pressure test due to delayed compressive strength development and relatively high permeability of set cement stone. Failure to meet those criteria's result in remedial cementing operations and delay of putting wells in production. To overcome this challenge new lightweight cement system based on optimized particles size distribution is successfully introduced for primary cementing of production casing on Verkhnechonskoe field. Implementation of the novel lightweight cement system with high solid volume fraction has allowed client to overcome highlighted issues. Rapid compressive strength development also helped in reduction of well construction time due to shorter wait-on-cement period.This paper outlines an approach based on the usage of optimized particles size distribution lightweight cement system in low temperature environment included three steps of cementing operation: design of cement system, implementation and evaluation results.
Horizontal drilling and multistage fracturing completions are becoming widespread practices in the development of Western Siberia’s low-permeability oil fields. More than 100 wells have been completed to date—with success from both operational and production perspectives. The majority of applications were applied in newly drilled wells, where it is possible to install openhole packers and frac ports for isolating fracture stages. The concept of multistage fracturing was transferred to old areas of brownfields, where sidetracks drilling was the main method of increasing oil recovery. Traditional sidetracks were associated with risks of production underachievement in low-permeability environments - even after stimulation treatments. The ability to drill sidetracks with a considerable horizontal section, and stimulating them with several fracturing stages would improve production significantly. However, slim wellbores of sidetracks significantly restrict completion option choice and abrasive perforating via coiled tubing (CT) becomes a universal enabler for multistage fracturing treatments. One of the greatest challenges in such a process is isolation between the stages. Fiber-enhanced proppant plugs were used for better proppant grains suspension, which sets the plug in the most efficient, homogeneous way. The first well was recently completed with this method. Three stages of fracturing stimulation were performed with CT abrasive perforation; fiber-enhanced proppant plugs were placed at the tail-in of the first two fractures. In both of the fractures, reliable isolation was achieved at first attempt. After all three stages were placed, wellbore cleanout with CT was performed, followed by nitrogen kickoff. Oil production has exceeded expectation by 30%. Multistage fracture (MSF) stimulation in the horizontal section of a sidetrack well completed with cemented liner with the utilization of abrasive perforating and fiber-enhanced proppant plugs has demonstrated unique value, as it is the only effective solution currently available for these conditions. The decision-making and candidate-selection processes, execution and lessons learnedare described.
The development of arctic resources requires wells to be drilled, cased, andcemented through permafrost. Permafrost presents unique challenges, especiallyto cementing operations, requiring a cement system with the capability toperform in the subfreezing permafrost environment. The performance required isthat the cement provides isolation, exhibits low heat of hydration, and setswith sufficient strength to provide casing support. There are also specifictesting requirements detailed in API recommended practices. In the polar region, there are several approaches used in the design of cementsystems. The approaches used in Russia, Canada, and USA (Alaska) areillustrated. The design considerations take into account local conditions andrequirements and use knowledge from cementing practices employed in thedrilling industry. It is important to understand the current cementing practices in use withinthe arctic region. This will allow future improvements as more developmenttakes place and the resources become exploited. Introduction To be successful, hydrocarbon resource development in arctic regions mustmeet the challenges posed by drilling, casing, and cementing wells throughpermafrost layers in the remote arctic environment. The Russian Far East, forexample, is almost completely covered in permafrost and holds significant gasreserves that remain largely untapped due to the remoteness of the area and thecomplexity of drilling through the permafrost layers. Offshore operations areadditionally impacted by sea ice, which does not directly affect cementingoperations; however, the short operational window certainly requires detailedplanning and reliable performance. The remoteness of arctic locations affects all aspects of development, impacting overall logistics: access, timing, and materials delivery andstorage. In addition, several of the challenges faced during the initialdevelopment phases affect the subsequent cement job and cementing practices. These challenges need to be addressed as part of the overall development plan;they include borehole maintenance, casing centralization, and mud conditioningand removal, and all require careful consideration of the permafrost.
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