Abstract

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.

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