概率法在油气储量不确定性分析中的应用

Application of probability method to uncertainty analysis of oil and gas reserves

概率法作为一种油气资源评估方法,在国内外得到越来越广泛的应用,它可以提供储量概率分布曲线或不同可靠程度的储量数据。涠洲A油田油气勘探获得重大突破,储量巨大,但在评价阶段探井未钻遇油水界面,含油饱和度等储量计算参数亦存在不确定性,导致地质储量预测存在一定的不确定性。文中以随机变量为对象,以概率法为理论基础,分析各参数不同分布函数对地质储量计算结果的影响,经组合计算得到地质储量的期望曲线,最后将概率法与确定性容积法计算结果进行对比。研究表明:含油面积、油层有效厚度样点较少,适合三角分布函数输入,其取值重点考虑区域统计规律认识;孔隙度和含水饱和度样点多,各种分布函数对储量计算结果均影响较小。概率法P90与确定性容积法计算的探明储量接近,而概率法P50与确定性容积法计算的探明与控制储量之和较接近,说明油田目前采用确定性容积法计算的储量比较可靠。

As a method of oil and gas resources evaluation, probability method has been widely used in China and abroad. It can provide a probability distribution curve of reserves or provide different reliable reserves figures. Weizhou A Oilfield has made great breakthroughs in oil and gas exploration and has huge reserves. However, during exploration stage, oil-water contact has not been substantiated, and there are uncertainties in the calculation parameters of reserves such as oil saturation, which leads to the uncertainties in reserves. Based on probability theory and random variables, this paper analyses the influence of different distribution functions of parameters on the calculation results of reserves, obtains the expected curve of reserves through combination calculation, and finally compares the calculation results of probability method with that of deterministic volume method.The results show that the sample points of oil-bearing area and effective thickness are fewer, which are suitable for triangular shape input. The recognition of regional statistical law is the key factor in the selection of oil-bearing area and effective thickness. There are many samples of porosity and water saturation, and various distribution functions have little influence on the calculation results.The probabilistic method P90 is similar to the deterministic volume method in proven reserves, while the P50 is close to the sum of proven and probable reserves, which shows that the reserves calculated by deterministic volume method are reliable.