川东石炭系天然气富集的水化学条件

HYDROCHEMICAL CONDITION OF NATURAL GAS ENRICHMENT IN EAST SICHUAN CARBONIFEROUS SYSTEM

徐国盛 刘树根 张英俊 张龙腾

Xu Guosheng Liu Shugen Zhang Yingjun Zhang Longteng

据100多口井水质分析,川东地区石炭系地层水具有浓度高、正变质程度深的特点。绝大部分地区地层水以氯化钙水型为主,局部存在重碳酸钠和硫酸钠水型。石炭系地层水化学场经历了由同沉积海水→剥蚀期淋滤水→埋藏期高矿化度浓缩变质水→气田伴生水的演化过程。矿化度高值区为天然气聚集的有利区带,氯化钙水型有利于天然气的聚集与保存。当地层水钠氯比≤0.65时,一般都含天然气,脱硫系数<1时(膏盐区除外)天然气的保存条件较好。

According to the analysis of water quality of more than 100 wells,the formation water of the Carboniferous in east Sichuan possesses high density and high direct metamorphic degree.The formation water in most parts of the study region is CaCl type,and the water in local places is NaHCO and NaSO-types.The formation water underwent the process of contemporary sea water→erosion leaching water→condensed metamorphic water with high mineralization in buried stage→associated water in gasfield.The places containing high mineralized formation water are favourable for gas accumulation;the places containing CaCl-type water are favourable for gas accumulation and preservation.When Nal/Cl ratio of formation water is ≤0.65,natural gas could be found;when desulphuration index is less(except gypsum and rock salt distributed area)than one,gas preservation condition is favourable.

10.11743/ogg19990104