致密砂岩储层气水分布特征及其主控因素——以天环坳陷北段上古生界为例

Gas and water distribution characteristics and its main controlling factors of the Upper Paleozoic tight sandstone reservoirs in the northern Tianhuan depression

为阐明致密砂岩储层气水分布特征及其主控因素,以天环坳陷北段上古生界致密砂岩储层为例,综合试产资料、气驱水核磁共振、圧汞等分析手段,在储层基本特征分析基础上,系统研究了天环坳陷北段山1-盒8段地层水赋存特征和气水分布规律,总结了气水分布规律的主控因素,认为多因素控制下山1-盒8段气水空间分布差异显著,纵向上孤立分布,平面上零散分布.研究结果表明:1)山1-盒8段地层水为氯化钙型IV与V类,孔喉半径截止值0.06μm和0.20μm将地层水产状划分为束缚水、滞留水和可动水;2)平面上,山1段产水层较局限,仅分布在中部砂带;盒8段产水层分布较多,产水量较高,全区仅在东北和西南部分井未产水;纵向上,山1到盒8段,水层逐渐增多、厚度增大,且水层多以透镜状分布在孤立砂体中,其分布没有气层连续性好;3)现今构造与成藏关键期古构造对气水分布影响不明显,广覆分布的煤系烃源岩造成的油气不饱和充注、储层物性好坏及裂缝发育程度是制约着气水分布的主控因素,使得产气层多分布在裂缝相对不发育区,较大产水量井主要分布于裂缝相对发育区.

To elucidate gas and water distribution characteristics of tight sandstone reservoirs,samples from the Upper Paleozoic Shan 1-He 8 member in the northern Tianhuan depression were utilized to study the occurrence characteristics of formation water and controlling factors of gas and water distribution.Nuclear magnetic resonance(NMR)of gas drive water,mercury intrusion and trial production data are applied in the research on the basis of basic characteristics of the target reservoirs.Research shows that the spatial distribution of gas and water in the Shan 1-He 8 member reservoirs,significantly different under multi-factor control,is isolated longitudinally and scattered in plane.The results indicate that:1)The formation water of the Shan 1-He 8 member reservoirs is classified as the calcium chloride type IV and V.The cutoff values of pore throat radii of 0.06μm and 0.20μm divide formation water into bound water,retained water and movable water;2)The water-producing layer in the Shan 1 member is relatively limited and only distributed in the central sand belt in the plane.There are many water-producing layers in the He 8 member with high water yield,and only a few wells in the northeast and southwest of the whole region have not produced water.Longitudinally,from Shan 1 member to He 8 member,water layers gradually increase in number and thickness,and the distribution of water layers is less continuous than that of gas layers.Those water layers are mostly distributed in isolated sand bodies in lenticular shape;3)Paleostructure and structure in the present in the key period of accumulation have little influence on gas and water distribution.The unsaturated filling of hydrocarbon caused by the widely distributed coal-measure hydrocarbon sources,the physical properties of reservoir and the degree of fracture development were the main controlling factors of gas and water distribution.Most of the gas-producing reservoirs are located in the fracture relative undeveloped areas,while the larger water-producing wells are mainly distributed in the fracture relative development areas.