哈萨克斯坦南土尔盖盆地A区块岩性油气藏

哈萨克斯坦南土尔盖盆地A区块处于断陷湖盆缓坡带, 构造圈闭不发育, 寻找岩性-地层油气藏是勘探突破的关键。已有钻井结果显示, A区块岩性油气藏主要位于侏罗系, 其自下而上可分为5套地层：埃巴林组、多尚组、卡拉甘塞组、库姆科尔组和阿克萨布拉克组。通过对侏罗系储集层、烃源岩、储盖组合等方面研究, 认为目的层发育3种类型岩性油气藏：斜坡带前缘砂上倾尖灭型油气藏、水下分流河道孤立砂体型油气藏及河口坝孤立砂体型油气藏, 已发现的A12井油藏属于中孔中渗的斜坡带前缘砂上倾尖灭型油藏, 为油气自生自储和侧向运移共同作用的结果。综合分析油气成藏条件认为, 研究区成藏的主控因素为有效储盖组合。结合多种地质、地球物理勘探方法分析得出, A区块的油气远景区集中分布于区块中部和西侧斜坡。图5表2参19

Lithologic reservoirs in Block A in the South Turgay Basin, Kazakhstan

Block A in the South Turgay Basin, Kazakhstan, lies in a gentle slope zone of rifted lake basin, where structural traps are not developed, so it is important for explorers to find litho-stratigraphic reservoirs. The drilling records show that, in Block A, the lithologic reservoirs are in the Jurassic System, containing 5 formations from bottom to top: Aybolin, Doshan, Karaganshy, Kumkol and Akshabulak. Through the research on Jurassic reservoirs, source rocks and reservoir-seal assemblage, it is proposed that there are three types of lithologic reservoirs at target formation: reservoirs with sands updip and pinch-out at front of slope zone, reservoirs with isolated sands in underwater distributary channels, and reservoirs with isolated sands at mouth bar. Well A12 is discovered containing middle-porosity middle-permeability reservoir with sands updip and pinch-out at front of slope zone, which was affected jointly by self generation - self preservation and lateral migration of hydrocarbons. The comprehensive analysis of accumulation conditions shows that the effective reservoir-seal assemblage is the main controlling factor for accumulation. With several geological and geophysical methods, it is concluded that the prospects are lied in central and west parts of Block A.