哈萨克斯坦Marsel探区下石炭统致密气资源潜力及勘探前景

哈萨克斯坦Marsel探区下石炭统历经多年勘探未取得重大发现，资源发现结果与评价的资源量极不匹配。为重新认识该区致密气资源潜力，利用高频层序、测井、试油、地震等资料，对下石炭统烃源岩分布、储层岩性及物性、含气饱和度等地质参数进行了重新评价，采用蒙特卡洛模拟法和小面元容积法估算了下石炭统致密气资源量，并评价了资源的平面分布特征。结果表明，Marsel探区下石炭统谢尔普霍夫阶（C₁sr）和维宪阶（C₁v）有效烃源岩的分布面积可达1×104 km2，探区北部烃源岩w（TOC）普遍在1.2%以上，南部基本在0.2%~1.2%之间，均处于生气高峰阶段；储层主要为礁滩相碳酸盐岩，平均孔隙度约6%，渗透率多在10×10-3 μm2以下，与烃源岩互层接触，可形成大面积连续分布的致密气聚集。蒙特卡洛模拟法估算Marsel探区下石炭统致密气90%、50%、10%概率下的可采资源量分别为1 551亿，4 001亿，8 753亿m3。小面元容积法评价结果显示，Marsel探区下石炭统致密气分布面积达6 000 km2，可采资源量4 323亿m3，平均可采资源丰度为0.7亿m3/km2，属于特低丰度致密气资源，但北部ASSA、Terekhov、KNDK等"甜点区"可采资源丰度在0.8~2.5亿m3/km2。通过借鉴水平井体积压裂开采经验，优选"甜点"钻探提高单井产量，Marsel探区下石炭统仍有望实现效益开发。 

Tight gas resource potential and prospect of the Lower Carboniferous in Marsel block,Kazakhastan

The amount of discovered resource is not in consistence with resource evaluation results at all, which leads to little significant breakthrough in tight gas exploration of the Lower Carboniferous in Marsel block of Kazakhastan.Based on the analysis of high frequency sequences, well logging, oil testing and seismic data, the hydrocarbon source rock distribution, reservoir rock types and its physical properties, gas saturation of the Lower Carboniferous in Marsel block are reanalyzed.Both Monte Carlo Simulation Method and the finite method are applied, in order to reevaluate the tight gas resource potential and distribution in Marsel block.The results show that the distribution areas of effective source rocks of Serpukhovian and Visean can reach 1×104 km2.The TOC of source rocks is above 1.2% in the north and between 0.2%—1.2% in the south in Marsel block, all in the hydrocarbon generating peak stage.The reservoirs are reefal-shoal facies primarily interlayered with source rocks in a large area, with an average porosity of 6%, permeability below 10×10-3 μm2, and saturation between 45%—65%.With Monte Carlo Simulation Method, the recoverable resources are evaluated to be 155.1, 400.1 and 875.3 billion cubic meters under the probability of 90%, 50% and 10% respectively.Based on the finite method, the tight gas accumulation area is 6 000 km2, recoverable resource is 434.6 billion cubic meters, and the average abundance of recoverable resource is 0.07×108 m3/km2 belonging to the low-very low abundance tight gas resource.However, in "sweet spots" like northern ASSA, Terekhov, KNDK, it can be between 0.08×108 — 0.25×108 m3/km2.By referring to horizontal well SRV fracturing experiences and "sweet spot" optimization to enhance single well production, economic benefit of exploration and development can be realized in the Lower Carboniferous in Marsel block.