鄂尔多斯盆地榆林气田马五_(1+2)气藏不同地质储量计算及采收率评价

The evaluation and calculation of different geological reserves and recovery ratio of Ma5_(1+2) gas reservoir in Yulin Gasfield of Ordos Basin

榆林气田下古生界马五_(1+2)亚段碳酸盐岩气藏,位于鄂尔多斯盆地靖边古潜台东侧,是靖边气田已开发的马五_(1+2)气藏向东的继续扩展,下古生界储层钻遇效果、生产特征显示良好开发潜力。由于储层非均质性较强以及气田开发早期资料不够丰富、井网密度相对较低等原因,导致提交的探明储量存在一定程度的误差。同时,气田在滚动开发过程中,避开了储层薄、物性差区域,故实际动用地质储量与早期提交的探明地质储量存在差异,影响了采气速度、采出程度及采收率等开发指标计算结果的准确性。针对存在的问题,采用多种方法,将气藏划分为相对独立的流动单元,通过落实各流动单元含气面积及储量,扣除了含气面积内未开发区域,核实得到的实际动用地质储量,更加准确可靠。同时,运用多方法计算气井动态地质储量,采用面积加权法与流动单元法计算气田动态地质储量,在此基础上,计算出储量动静比,为准确计算采收率奠定了基础。通过经济评价及气藏工程研究,确定气田废弃产量、废弃地层压力,结合气田动态地质储量及储量动静比,最终确定不同地质储量对应的采收率。对比分析认为:探明地质储量采收率误差大;核实动用地质储量采收率切合实际,具横向可比性;动态地质储量采收率排除了不可渗流的无效储量,更加科学、实用。

Lower Paleozoic carbonatite Ma51+2 gas reservoirs in Yulin Gasfield,located on the east side of Jingbian ancient submarine platform of Ordos Basin,which is the expanded part of the developed Ma51+2 gas reservoir in the Jingbian Gasfield.Under the effect of drilling and the production characteristics,the Lower Paleozoic reservoir shows good development potential.Because the heterogeneity of reservoir is strong,the data of early gas field is not rich enough,and the density of well pattern is relatively low.There is a certain degree of error in the proven reserves.At the same time,it is in the process of rolling development of the gas field.Because avoided the thin reservoir and the poor physical property,the actual use of geological reserves and the early submission of the proven geological reserves are different.This will influence the accuracy of the calculation results of the development index of gas recovery rate,recovery degree,recovery ratio and so on.In view of the problem,many methods are adopted to separate gas reservoirs into relatively independent flow units.By carrying out the gas-bearing area and reserves of each flow unit,it is more accurate and reliable to verify the actual geological reserves obtained by excluding the undeveloped area in the gas-bearing area.The dynamic reserves of gas wells are calculated by using many methods.The dynamic reserves of gas fields are calculated by area weighted method and flow unit method.On the basis of this,the dynamic ratio of reserves is calculated,which lays a foundation for accurate calculation of gas recovery.According to the economic evaluation and gas reservoir engineering research,the waste gas and waste formation pressure will be confirmed in the gas field.Combined with the dynamic reservesand its ratio for the geological reserves,the recovery of the different geological reserves will be calculated finally.Through comparison and analysis,the geological reserves ratio are proved to be of greaterror.Itismorescientificandpractical to verify the geological reserves ratio to be practical,to have lateral comparability.The dynamic geological reserve ratio excluded the ineffective reserves of non-seepage,which is more accurate and reliable.