三湖坳陷北斜坡区岩性圈闭预测

Prediction of lithologic trap in the northern slope of Sanhu Depression

岩性圈闭作为三湖坳陷北斜坡区下一步天然气勘探的主要目标,能否有效识别并预测岩性圈闭成为制约气田下一步增产上储的关键.从区域地质背景和现今气田勘探生产概况入手,首先明确了岩性圈闭纵向发育的主要标准层位为K9—K13,进而分析了工区K9—K13层序地层及沉积微相发育特征,其中K9—K13包含2个水进体系域(K9—K10、K11—K13)和一个高位体系域(K10—K11),砂体沉积微相类型以滩砂为主,最后通过层序地层理论指导下的井间精细砂体对比,并结合K13构造等深图,确定了岩性圈闭纵向主要发育在K9与K11最大洪泛面附近,平面上主要分布在台东、涩东和驼西3个鼻隆区以及驼南、涩南和盐西3个斜坡区.

Lithologic trap is the main object of the further natural gas exploration in the northern slope area of Sanhu Depression,and therefore the effective prediction of lithologic trap is the key to the increase of gas-field reserve.By analyzing the regional geologic background and the current gas-field production status,it is held that lithologic trap mainly develops between log marker K9 and K13 in vertical direction.Based on the analysis of sequence stratigraphy and sedimentary microfacies characteristics of log marker K9-K13,it is found that log marker K9-K13 consists of two transgressive system tracts(K9-K10 and K11-K13) and one highstand system tract(K10-K11),and the sedimentary microfacies of sandbody is mainly beach sand.Finally,the distribution range of the lithologic trap is determined on the basis of fine inter-well sandbody contrast under the guide of sequence stratigraphy theory and structure isobath map of log marker K13:the lithologic trap develops mainly near the maximum flooding surfaces K9 and K11 in vertical direction,and in the plane it mainly distributes in three nose uplift areas(Taidong,Sedong and Tuoxi) and three slope areas(Tuonan,Senan and Yanxi).