川西新场气田须二气藏水体动态分布与水化学特征

为直观、详细地论述川西新场须二气藏气井产出水状况，文中将气井产出水分为凝析水、地层水、夹层水或残留地层水3个大类。研究发现，构造主体部位的气井在产出地层水之前大多经历过一段较长时间的凝析水产出阶段；之后南北部边水才侵入构造主体；而构造主体的东西部产出夹层水或残留地层水。其主要原因是随着气藏开采，地层能量下降，边部水体沿着南北走向断层入侵到高部位，使得高部位气井大量产水；至于构造主体的东西部，由于远离断层，微裂缝不发育，气井产水量较少。总体而言，由于产出水类型不同，其水化学成分亦存在较大差异，表现为凝析水矿化度低、地层水矿化度高、夹层水或残留地层水的矿化度则介于两者之间。气井产出水化学性质差异性源自水—岩反应环境、流体压力、天然气浓度以及pH值等影响因素的变化。因为随着气井天然气的采出，流体压力下降、天然气浓度降低，盐离子的溶解度亦降低，所以构造主体产出地层水时，其Ca²⁺浓度较南北边部的要低，水体中出现少量Ca沉淀。

Water Dynamic Distribution and Chemical character in Xu2 Member Gas Reservoir of Xinchang Gas Field,Western Sichuan Basin

For intuitive and detailed discussion of the gas well water of Xu2 reservoir in the Xinchang gas field of the western Sichuan basin,we divide the output water into three categories of condensate water,formation water and interlayer water (or residual formation water).The results indicated that all of the gas wells in the structure of the main parts have experienced a longer period of condensate water output phase before the formation water output,and then the edge water from the north and south sides begins invading to the structure main parts;in contrast that the east-west gas wells of the structure of the main parts may output the interlayer water or residual formation water.Because the sequence energy decrease with gas reservoir developing,and the edge of water begins invading into the structure of the main parts along the north-south fault,causing the gas wells in the structure of the main parts product a large number of water.Micro-cracks in the east-west gas wells of the structure of the main parts are not developed owing to far away from the fault,gas wells have little water.Overall,the different types of produced water are associated with the different chemical compositions of water,with presence of low salinity in the condensate water and high salinity in the formation one,the interlayer water or residual formation water salinity falling between two members above.The differences of water chemical characters depend on water\|rock interaction environment,fluid pressure,gas concentration,pH value,etc.With gas taken out,fluid pressure drops,gas concentration decreases,and salt ion solubility reduces.So the Ca ion concentration in the formation water of main part structure is lower than that in the edge of the north\|south,with occurrence of Ca precipitation.