Liaohe Rift Shuguang Oilfield Du 239 Dalinghe Reservoir To Convert The Study Of The Development Approach

Dalinghe reservoir of block Du239,Shuguang oilfield, Liaohe depression, belongs to heavy oil reservoir which is typically of medium thickness and layered. It was put into production in 1990 by cyclic steam stimulation. Since 1996, through the optimization steam injection parameters, as well as layer adjustment and re-perforation, side-tracking, selective injection and production after the middle stage of cyclic steam stimulation, the producing degree of reserves has been improved, and good CSS result has been achieved. The development index of CSS stage is higher than that of similar reservoirs and plan index. This block has the highest ratio of total oil produced to OOIP (49.1%) among the heavy oil blocks in Liaohe oilfield produced by thermal recovery. At present, the actual well spacing in Dalinghe reservoir of block Du239 is 100m, the main part has been infilled to 70m. The average cycles of steam stimulation is 9.5, the major problems in the block are low formation pressure and inter-layer problem. The potential of continuous CSS is very limited. There will be almost no economic benefit by continuous CSS. How to substitute oil production is a serious problem. The development potential of CSS is analyzed by using measured pressure data, steam injection profile, heating radius equation, mathematical statistics, numerical simulation and reservoir engineering technology, and by starting with Dalinghe reservoir CSS development response and current reservoir performance. 3D geological model is established according to reservoir characteristics. Numerical simulation is conducted on the basis of production history match. Lateral and vertical residual oil is studied by using material balance method, numerical modeling and various monitoring data. Meanwhile, the result of pilot test is evaluated. It is thought that steam slug drive and intermittent steam drive have played an important role for reservoir stabilization. Finally, through comparison of various potential tapping methods, the production-substitute technology is optimized for this block. The main research achievements are as following:(1) After many years' CSS development, good response has been achieved. In the mid-late stage of CSS, reservoir pressure declines, the development response becomes worse. Continuous recovery by CSS would only have an interval ratio of total oil produced to OOIP of 4.3%.(2) Comprehensive study shows that steam drive is the main trend of converting development scheme in Dalinghe reservoir of Du239.(3) The conversion area adopts 70m well spacing, inversed nine-spot pattern, 9 well groups are arranged for one strata series (up-hole recovery) .Steam drive can produce for 13 years, cumulative oil production will be 68.2 × 10~4t.(4) According to actual sale price, the internal earning rate of the plan is 10.44%, which is higher than the base earning rate of 10% specified by the nation and incorporated company. Financial net present value is 298.4, the payback period is 6.4 years. There is certain economic benefit, but the risk resistance ability of the plan is weak.