Recently drilled exploration well at Chayandinskoye Gas Condensate Field in East Siberia, where at the moment exploration drilling is at the final stage, was selected as a candidate to evaluate effectiveness of hydraulic fracturing stimulation to boost the production. During the production logging and the well test on the pilot vertical section, three prolific zones were identified for further development. As a result of several discussions with the Client and based on the preliminary data analysis, the decision was made to proceed with hydraulic fracturing treatment. Due to the remoteness of the field, unique and complicated geology and reservoir properties, it was clear that the single contactor is required who has a relevant experience and technology being capable to address the challenges and provide an integrated approach. This approach included designing fit-for-purpose well completion, multistage selective hydraulic fracturing and coiled tubing applications inclusive of capability to perform real-time downhole measurements to monitor and evaluate complex multiphase flow profile. Company's completion segment had introduced and run 168-114mm combined premium-port liner down to 2034m MDDF equipped with 3 ports able to be shifted in open/close position, and hydraulic open-hole swelling packers to isolate annular. This type of completion allows selective or combined production from all the zones. Moreover, it enables selective stimulation of each zone, as well as selective or combined production well testing. In case of water breakthrough, knowing which zone is contributing to the water production, the premium-port can be shift closed to prolong the production without the immediate need to perform costly water shutoff treatment. Historically hydraulic fracturing has been a very effective way of increasing production in low permeability reservoirs. Based on the job design, three treatments were performed with 39t, 95t and 20t accordingly. Coiled Tubing services performed debris and residual proppant wellbore cleanout, multiple shifting of premium-ports, nitrogen kick off, and real-time downhole measurements of bottomhole pressure, temperature and production logging. The remoteness of the gas condensate field and the limited timeframe created additional challenges in terms of logistics, equipment and chemicals mobilization. It was clear that the proper preparation and planning were the key to succeed. Needless to mention that the company state-of-the-art technologies, competent personnel and close collaboration between the segments and the Client were the essential part of the equation.

This paper describes the integrated approach to decision making on the optimized horizontal well completion with multistage fracturing (MSF) based on petrophysical, geomechanical and numerical modeling. This approach is pertinent in case of insufficient target exploration including absence of a full scale geo&hydromodel (FSGHM). The basic work process of the proposed approach is based on consistent efforts of a petrophysicist, geomechanical engineer, fracturing engineer and reservoir engineer and thus includes petrophysical and geomechanical modeling, fracturing design, numerical modeling and final planned well flow rate evaluation. The role of geomechanics in the production chain is to determine zones with the lowest and the highest fracture gradients to control fracture location and analyze fracture geometry. The basic objective of the proposed approach is to develop a set of recommendations to select: Optimized frac sleeve spacing to increase production during a certain period of well production;Optimized proppant injection volume in general and for each fracture;Recommended horizontal well paths for efficient multistage fracturing completion and reduction of the most probable risks;Frac sleeve placement with provision for the horizontal well path through the section (vertically) to optimize fracture initiation points and maximize reservoir coverage. Besides, according to the base history, costs of new target development using available production technologies can be estimated based on the completed work package. An additional objective of this approach is identification of interdependent parameters for further facilitation of downhole surveys and laboratory studies and excluding of non-informative methods. This paper gives an example of the developed method application for a prospecting and appraisal well at one of the West Siberian fields with a target characterized by extremely low permeability and uncertainty.

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.