疏松砂岩气藏水平井开发难点及对策——以柴达木盆地台南气田为例

柴达木盆地台南气田储层埋藏浅（833～1 740 m），成岩性差，岩性疏松，泥质含量高，非均质性强，单气层厚度为1～3 m且层数多，气水分布复杂，使得水平井开发存在造斜困难、井眼坍塌、轨迹失控等风险。为此，就已完钻的40余口水平井从设计、施工、开发效果等方面分析、总结了水平井在该气田的推广应用情况，并对水平井钻井状况、目的层特征、井眼轨迹与钻遇率等进行了评价；结合水平井的生产现状进行了产量、压力、出水和出砂等动态分析，开展了产能与产量评价，以及出水、压降原因剖析和单产递减特征的描述等工作；对不同储层类型、不同水平段长度和不同井型的水平井，以及水平井与直井的产量、投资等进行了综合对比。最后提出的开发对策是：搞清地质条件，提高地质认识，把握好井眼轨迹，合理配产，现场生产管理到位，做好防砂控水，建好配套技术监控体系。

Technical difficulties and proposed countermeasures in drilling horizontal wells in loose sandstone gas reservoirs:A case study from the Tainan Gas Field,Qaidam Basin

Gas reservoirs in the Tainan Gas Field, Qaidam Basin, are featured by shallow burial depth (833 1740 m), low diagenetic ability, loose lithology, high shale content, strong heterogeneity, and multiple gas pays with the thickness (1 3 m) of a single layer, as well as a complex distribution of gas and water. All those above will lead to great difficulties in horizontal well drilling such as trouble in the angle building, risk of borehole collapse, and the well trajectory's being out of control. In view of this, based on the case histories from more than 40 completed wells, this paper analyzes and summarizes the application of horizontal well drilling in this gas field in terms of design, operation, production performance, and so on. Also, this paper evaluates the horizontal drilling performance, characteristics of pay zones, well trajectory, drilling catching ratio, etc. According to the production status of those horizontal wells, a dynamic analysis of production, pressure, water and sand invasion was made to have an evaluation study of the production capacity and output of wells, explore the reason for water production and pressure drop, and describe the single well's yield decline features. In addition, a comprehensive comparative analysis was performed in the aspects of various reservoir types, different types of horizontal wells with diversity of lateral sections, and difference in production and investment cost between vertical and horizontal wells. In the end, the development countermeasures are presented: having better geological understandings, keeping a good grasp of well trajectory, allocating the production in a rational way, managing the on site production effectively, having a good control of the sand and water production, and establishing a comprehensive supervision system for the supporting techniques.