Reserves Calculation And Economic Evaluation Of Y99Block In Yanchang Oilfield

Y99block in Yanchang oilfield is located in the east of Ordos basin, Chang6reservoir distribute in underwater distributary channel sand of delta front and distributary channel sand of delta plain. The oil-bearing sand body of Chang6reservoir is more, composite shall and is a typical lithologic reservoir. Meanwhile, the characteristic of reservoir is oil-water mix store and on noticeable side of bottom water. So, the developtment of Chang6reservoir is difficult. Out to locate oil geological reserves for study area, use volume method to calculate proven oil geological reserves, and carry on the development concept design and economic evaluation, which can improve oilfield development level and be of great significance.The oil geological reserves calculation widely use volume method. Hard to volume method to calculate geological reserves, but should use dynamic method and the probability method. The Chang6reservoir of Y99block in Yanchang oilfield belongs to early stage of scrolling development. Therefore, this study used volume method for the reserves calculation is more reasonable. Using volume method for the reserves calculation, the Chang6oil reservoirs of Y99block is divided into three calculation units of Chang61, Chang62, Chang63, which is as one calculation unit in the plane. Using the volume method for the reserves calculation, oil geological reserves of Chang6oil reservoir of Y99block is761.51×104t (921.93×104m3), dissolved gas geological reserves is0.92×108m3, composite oil area is17.53km2. According to the oil reservoir type and properties, including petrophysical property, fluid property, rock and fluid related properties, and devopment condition, the oil technology recovery ratio under natural energy mining is11%, the oil technical recoverable reserves is83.77×104t (101.41×104m3), the dissolved gas technical recoverable reserves is0.10×108m3.The evaluation method of economic recoverable reserves include cash flow method, economic limit method and analogy method. According to production dynamic data of Chang6oil reservoir of Y99block, use economic limit method and cash flow method, comprehensive analysis that the economic recovery is10.3%and oil economic recoverable reserves is 78.43×104t (94.96×104m3).Accarding to exploration and development degree and geological research, the reserves category is defined as proved undeveloped reserves. Comprehensive assessment indicates that Y99block is a conventional and small oilfield, is the lithologic reservoir of elastic and dissolved gas driven, where the output is low, reserves abundance is also low and sulfur elements in oil is less. The Chang6reservoir buried depth is in middle-shallow and the characteristic of reservoir physical properties is low permeability and low porosity. By economic and technical indexes, the Chang6reservoir of Y99block belong to low benefit oilfield. But exploitation technology and managerial approach is fit to the oilfield production, after-tax internal rate of return which is28.79%greater than the industry benchmark rate of return which is12%. Therefore, the oilfield can get a certain economic benefits.