In the article presented 2 years of experience gained during multi-stage hydraulic fracturing (MSF) on 17 wells, by means of coiled tubing (CT) without lifting it to the surface, performed in years 2017 – 2018 on Vinogradova oilfield, KhMAO, Russia. In 2017 it was successfully implemented innovative technology, where fracturing operations are combined with coiled tubing (CT) operations and are run together with CT inside the well. Current method is based on operating reusable fracturing ports, where opening and closing is carried out using coiled tubing with subsequent performace of MSF along the CT/Tubing annulus. During these jobs, considerable experience was gained, the technologies were optimized and raised issues solved, including excessive abrasive wear of the coiled tubing pipe, leaks, etc. Vinogradova oilfield is a unique oil-saturated low-permeable reservoir with a small effective thickness, characterized by considerable stratification and gas-saturated porous layers. MSF technology demonstrated high efficiency and proved its reliability. Starting from February 2017 till June 2018 it was 17 wells accomplished, where 246 fracturings were carried out. All the wells were successfully commissioned. The implementation of innovative approaches to multi-stage hydraulic fracturing while coiled tubing remains in the well, resulted in 2-fold work time reduction, while the amount of frac ports doubled per well. The time frame of CT work between fracturing stages was minimized from 4 to 1.5 hours. During the job on one of the wells, it was encountered a leak in the completion (liner) in the shoe area, in order to continue MSF job, the isolation packer was run and temporary installed, which allowed to accomplish the operation. The performance of MSF technology without lifting coiled tubing to the surface proved its efficiency and economic feasibility, becoming more and more popular among operating companies, it has great potential for future implementation both in Russia and in the rest of the world. The area of distribution and application of MSF using CT is growing every year, the most relevant technology found in oil fringe with a gas cap or bottom water. The accumulated experience in this project creates the basis for the wide introduction and application of technology on other projects
Today, when most reservoirs have low productivity, the question of whether hydraulic fracturing can be applied to the oil rims becomes very important. During hydraulic fracturing at Novoportovskoe field, the operator was faced with a complex geological model of the reservoir characterized by an absence of strong barriers and minor contrasts in stress between interlayers associated with high risks of breakthrough into the gas zone. An outstanding example of oil rim stimulation and application of new technology was a project in Novoportovskoe field where 30- and 27- stage multistage fracturing operations (MSF) were successfully performed with a shifting ports completion operated by coiled tubing. Currently, oil and gas companies are increasingly demanding technical and technological aspects of the MSF, where the determining factors are the efficiency of operations, the number of stages, the length of the horizontal part of the well, the possibility of refracturing, and ability to open / close sleeves after operation for water and gas shut-off. The experience gained shows the possibilities of modern technologies, where the use of coiled tubing enables meeting the high requirements and also expanding the boundaries of the application. The 30-stage boundary was successfully overcome and allowed to increase the formation coverage by means of more fracturing stages. At the same time, the completion method made it possible to perform MSF without pulling the coiled tubing out of hole and to use all the capabilities and benefits of CT in the case of a screenout (SO). The teamwork between the customer and several of the contractor's product lines enabled successful completion of the integrated project under the difficult geological and climatic conditions of the Novoportovskoe field, which is located beyond the Arctic Circle. An optimized concept of MSF with the use of re-closable full-pass hydraulic fracturing sleeves, operated by a single-trip coiled tubing-conveyed shifting tool was developed and implemented. The following results were achieved: In one week, 57 hydraulic fracturing stages were completed.Hydraulic fracturing stage time was reduced by 63%.The number of stages per well increased by 43%.The gas factor for storage was reduced from that of previous fracturing operations. The integrated method of multi-stage hydraulic fracturing allowed achieving effective fracture coverage to increase the recoverable reserves, while preventing fractures in the gas cap and bottom water. The sliding sleeves MSF technology, operated by coiled tubing without pulling it out of hole, is applicable to further operations in the region and worldwide. This paper describes the experience, lessons learned, and best practices gained at the Novoportovskoe field while deploying a novel application of MSF for oil rim deposits where CT was used as the key enabler. It also describes the first success worldwide in closing of sleeves after 1 year of well production. The well was completed in December 2017 with a 30-stages, and in 2018, after a year of production, logging showed a gas break through which required eight sleeves to be closed. All eight sleeves were successfully closed. This method can be applied to other oil and gas fields, where the construction of horizontal wells with MSF is the main development strategy.
The geology of Eastern Siberia formations is unique. In particular, producing formations of the Chayandinskoye field have extremely low temperatures 46 -55° F (8 to 13°C). The field is currently in the exploration stage. Geological properties of the formations vary significantly, and it is necessary to define appropriate methods of well construction and completion prior to switching to a field development stage. One of the prospective options is to implement hydraulic fracturing in low-permeability areas of the Chayandinskoye. A multistage stimulation campaign was executed to test the efficiency of hydraulic fracturing in subhorizontal multilayer well. Coiled tubing was involved in operating controllable frac ports, well kick-off and inflow profile recording using proprietary technologies. The project is one of the first gas fracturing campaigns in Eastern Siberia. The well completion configuration combined 6-5/8- and 4-1/2-in. liners, equipped with three frac ports that allow multiple opening and closing. This completion makes possible to get separate or combined inflow from producing layers. The coiled tubing fleet made several runs for frac port manipulation, wellbore cleanout of debris and residual proppant, and well kickoff until production achieved the natural flow regime. Gas wells of Chayandinskoye field have a potential to form gas hydrates at formation conditions. Therefore, special inhibitors at high concentrations were introduced in stimulation fluid and during wellbore cleanout and kickoff. Coiled tubing minimized the hydrate issues from production start up until stable gas flow was reached. A wireline bottomhole assembly for inflow profiling and downhole pressure and temperature recording was used to obtain precise measurements of multiphase flow in the sub-horizontal wellbore. The tool was run via coiled tubing, and fiber optic telemetry transferred data from the bottomhole in real time. The remote location of the field and limited operational timeframe due to winter road conditions generated additional difficulties in equipment logistics. As a result, the planning and preparation phases were crucial for project execution. Results have shown that fracturing as a method of field development is effective, but requires a complex preparatory stage in the laboratory and further optimization to local logistics and geological conditions. Coiled tubing services are an integral part of the completion process. By combining fiber optics telemetry and multiphase flow scanning, engineers could identify underperforming frac ports and propose prompt remedies. The technologies used in the well also enabled production testing in the exploration well in various regimes – separately from each formation, and combined. Results from the complex exploration workflow will be used to make decisions on overall field development.
An integrated approach was applied for production enhancement of the upper and lower shaly sandstone reservoirs of the Ignalinsky and Tympuchikansky fields in the Leno-Tunguska oil and gas province of the East Siberian Basin, Russia. The approach includes both comprehensive laboratory studies and a direct strategy of hydraulic fracturing design, as well as solutions to obtain optimum well performance. The approach can be implemented in future prospects and can form part of the strategy for future development in the region. Extensive laboratory research was performed to select the proper fluid for proppant transport that could withstand all the complicated terrigenous conditions within the fields. One of the main challenges was rheological suitability of the fluid at low reservoir temperatures. The laboratory studies were important for identifying the best fluid for fast fracture cleanup while optimizing the sand-carrying capacity of the fracturing fluid. The hydraulic fracturing design incorporated calibrated petrophysical and geomechanical analysis with actual fluid rheology characterization taken from laboratory test results. The laboratory work confirmed that the reservoir rock was water sensitive, with a significant presence of clay minerals including kaolinite, montmorillonite, and montmorillonite mixed with illite. A new generation of clay stabilizer was used to address this sensitivity. In addition, an enzyme breaker was used with the objective of effectively breaking the fracturing fluid at low reservoir temperatures. The fracturing operations that were performed during two winter campaigns resulted in high starting and operating production rates. The treatment designs incorporated a linear gel pre-pad stage prior to the crosslinked pad stage in an effort to extend fracture half-length while reducing the risk of the fracture growing in height into overlying gas-saturated layers. The results of the design efforts were analyzed using logging and fracture treatment data, which demonstrated that the design was effective in avoiding the gas-saturated formation. Overall, 23 hydraulic fracturing operations were done in five wells at Ignalinsky and Tympuchikansky fields for the B10 and B13 formations. Production results were analyzed, and further optimization paths were identified. The study breaks new ground in enhancing the hydrocarbon extraction from low-temperature shaly sandstones with mixed wettability, not just with terrigenous reservoirs within the above-mentioned fields, but also with other reservoirs of a similar geological context, primarily the Leno-Tunguska oil and gas province of the East Siberian Basin, Russia. This is especially important in view of the depletion of oil reserves in Western Siberia and the growing interest in the development of hydrocarbon fields in Eastern Siberia.
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