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苏里格气田盒8下亚段气藏纵向多期河道砂体依次切叠,横向同一期次内不同河道砂体相互拼接、同一河道内辫状水道砂体与心滩砂体交错切割,形成了层次复杂的辫状河储层。沉积层次的复杂多样导致储层内部发育不同层次的隔夹层,其产状、规模及发育位置均存在较大差异。正确识别并“有效避开”这些隔夹层从而达到提高砂体钻遇率的目的是辫状河储层水平井地质导向的重点和难点。以苏里格气田中区下二叠统石盒子组盒8下亚段储层为研究对象,运用Miall的储层构型基本理论,将研究区隔夹层划分为3个层次:1垂向层间隔层;2侧向河间泛滥泥;3单砂体内部夹层。对不同层次隔夹层进行了成因分析,分别阐述了其空间分布、测井响应特征,在此基础上提出了相应的水平井地质导向策略:钻遇垂向层间隔层适当角度(<1.5°)穿越泥岩;钻遇侧向河道间泥质体大角度(2°~3°)快速穿越或实施侧钻;钻遇单砂体内部夹层略微调整井斜(<0.5°)。2014年该套方法在苏里格气田某区块进行现场应用,与邻区相比砂岩钻遇率、有效储层钻遇率分别提高了5%和3%,具有一定的推广价值。
Longitudinal multistage channel sand bodies in the lower sub-block 8 of the Sulige gas field are successively stacked, and the different channel sand bodies are spliced together in the same horizontal period. The braided channel sand bodies and the beach sand bodies in the same channel are alternately cut and formed A complex layer of braided river reservoir. The complexity and variety of sedimentary layers lead to the development of intercalation layers at different levels within the reservoirs, and their occurrences, sizes and developmental locations are quite different. The purpose of correctly identifying and effectively avoiding these intercalations so as to improve the rate of sand body drilling is the key and difficult point of geosteering of horizontal wells in braided river reservoirs. Taking the reservoir of the Lower 8th Member of the Lower Permian Shixianzi Formation in the Central Sulige Gas Field as the research object, the Miall reservoir basic theory is used to divide the study area into three levels: 1 vertical layer Interval layer; 2 lateral flood mud across the river; 3 sand body intercalation. Based on the above analysis, the geosteering strategy of horizontal wells is proposed: the appropriate angle (<1.5 °) between the vertical layers is drilled, Crossing the mudstone; drilling across the muddy body in the lateral channel quickly through a large angle (2 ° ~ 3 °) or carrying out the sidetracking; and drilling the well within the single sand body to adjust wellbore slightly (<0.5 °). In 2014, this set of methods was applied on site in a block of Sulige Gas Field. Compared with the adjacent area, the drilling rate of sandstone and the rate of effective reservoir drilling increased by 5% and 3% respectively, which is of certain promotion value.