苏里格气田西区地层水成因、分布规律与控制因素

苏里格气田西区气井产水严重，地层水成因、分布规律及控制因素不明确，成为制约该区致密砂岩气开发的关键科学问题。在大量测井数据、生产动态数据收集的基础上，分析了苏里格气田西部地层水性质及地球化学特征，结果发现:地层水矿化度高，整体属于盐水；水型主要为CaCl₂型；pH值范围为6~6.9，呈弱酸性。分析认为:1）地层水主要为埋藏变质水成因，地下水保存条件好，从而有利于天然气的保存；2）研究区地层水的分布具有下气（山₁段）上水（盒₈上亚段）、东气西水的空间分布规律；3）地层水主要有构造低部位水（Ⅰ型）、低渗带滞留水（Ⅱ型）、孤立透镜体水（Ⅲ型）三种分布类型；4）研究区西部构造低部位含水较多，类型为Ⅰ型，盒₈下亚段砂体边部、缓坡带多形成低渗带滞留水（Ⅱ型），盒₈上亚段、研究区东部构造高部位多为孤立透镜体水（Ⅲ型）；5）苏里格气田西区致密砂岩气具有近源成藏的特点；6）控制气水分布的主要因素包括气源岩供烃潜力、储层物性、垂向运移距离、构造位置等；7）明确地层水成因，把握地层水分布规律与控制因素、建立气水分布与天然气成藏模式，可以有效指导气田的避水开发。

Origin,Distribution and Controlling Factors of Stratigraphic Water in the Western Sulige Gas Field

Severe water production of gas wells in the western Sulige gas field restricts the development of gas production from the dense sandstone in this area. The unclear nature of the origin， distribution and behavior of the groundwater have been a a key scientific problem. In this study， the stratigraphic water properties and geochemical characteristics were analyzed from a large amount of logging data and the collection of dynamic production data. The results show that （1） the stratigraphic water is highly saline at the level of brine， as a whole； （2） the water is mainly CaCl₂ type； and （3） its pH is weakly acid. The following conclusions were drawn from the study. （1） The stratigraphic water stems mainly from a buried metamorphic source， and the good state of its preservation in the groundwater is also beneficial for the preservation of natural gas. （2） The spatial distribution of the stratigraphic water is consistent with that of the lower gas （S₁ sub-member） and upper water （H₈u sub-member） and east gas?west water. （3） In the study area， the water is mainly of three types: low-structure water （type I）， low permeability zone retention water （type II） and isolated lens water （type III）. （4） The lower part of the western structure contains mostly type I water； the H₈l sub-member， the edge of the sand body and the gently sloping zone form the low-permeability zone that retains type II water； and the H₈u sub-member and the highest part of the eastern zone of the study area contain mostly type III isolated lenses of water. （5） Gas in the dense sandstone of the western Sulige gas field has the characteristics of near-source reservoir formation； and （6） the main factors controlling the gas?water distribution include the hydrocarbon supply potential of the gas source rocks， the physical properties of the reservoir， the vertical migration distance， and its tectonic location， among other factors. These findings， which have clarified the origin of the groundwater， its distribution and controlling factors， and have established the gas?water distribution and natural gas accumulation mode， can be used to guide water-avoidance in the gas field.