延安气田低渗透致密砂岩气藏效益开发配套技术

延安气田位于鄂尔多斯盆地东南部,与该盆地北部的气田相比,储层更薄、物性更差,气藏叠置关系复杂,加之地表为黄土塬地貌,储层地震预测难度大,现有的气田开发配套工程技术适应性差,亟须优化气田开发方式与开发技术。为此,延长石油集团经过近十年的理论研究和技术攻关,在储层预测、井网优化、钻完井、储层保护、压裂改造、地面集输等方面,形成了一套适合延安气田复杂致密砂岩气藏高效开发的关键技术体系:(1)融合多尺度静、动态研究成果,建立了基于动态知识库的有效储层预测技术,大幅度提升有效砂体钻遇率,实现了对厚度3～5 m稳定单砂体的准确追踪;(2)形成了以不规则菱形井网为基础,丛式井多层合采、水平井单层动用的混合井网立体动用模式,较规则井网井数减少6.9%,井网控制程度提高8%;(3)形成了易伤害塌漏同井储层高效钻井技术,有效提高了井壁稳定性、缩短了钻井周期,保护了储层;(4)实现了直/定向井一趟作业多层大跨度压裂、水平井CO_2+水力压裂技术,单井天然气产量显著提高;(5)形成了以井下节流、枝上枝井间串联和集中注醇为核心的黄土塬地貌中压集输技术,减少了工作量,缩短了施工周期,提高了经济效益。以上关键技术的应用,实现了延安气田低渗透致密砂岩气藏的效益开发,建成了年产气50×10~8 m~3的生产能力。

Technologies for the benefit development of low-permeability tight sandstone gas reservoirs in the Yan'an Gas Field,Ordos Basin

The Yan'an Gas Field is located in the southeastern part of the Ordos Basin, and its low-permeability tight sandstone gas reservoirs are characterized by thin reservoirs, poor physical properties and complex overlapping relationships. In addition, its surface is loess tableland, which makes it difficult to predict reservoirs by using seismic data. As a result, existing engineering technologies for gas field development cannot support the efficient development of this field. In order to optimize the development methods and technologies of the Yan'an Gas Field, the Yanchang Petroleum (Group) Co. Ltd. has developed to a set of key technologies suitable for the benefit development of this field concerning reservoir prediction, well pattern optimization, drilling and completion, reservoir protection, fracturing stimulation and ground gathering and transportation after nearly ten years of theoretical and technical researches. First, an effective reservoir prediction technology based on dynamic knowledge base was developed. It improves the drilling ratio of effective sandbody dramatically and achieves the accurate tracking of stable single sandbody in the range of 3–5 m. Second, a three-dimensional exploitation mode of mixed well pattern based on the irregular diamond-shaped well pattern was established. It includes the multi-layer commingled production of cluster well and the single-layer production of horizontal well. Compared with regular well patterns, the well number is reduced by 6.9% and well pattern control is increased by 8%. Third, high-efficiency drilling technology for vulnerable reservoirs with collapse and leakage in the same well was developed. It improves wellbore wall stability, shortens drilling cycle and protects reservoir. Fourth, the multi-layer long-span fracturing of vertical/directional wells in one operation and the CO2 and hydraulic fracturing treatment of horizontal wells were realized to improve single well production significantly. Fifth, the medium-pressure gathering and transportation system in loess tableland with downhole throttling, branch-on-branch inter-well tandem and centralized alcohol injection as the core technologies was established. It reduces workload, shortens construction cycle and improves economic benefit. In conclusion, these development technologies play a crucial role in the development, appraisal and productivity construction of the Yan'an Gas Field. Through the application of these key technologies, the benefit development of this field is realized with an annual natural gas production capacity of 50×108 m3. Furthermore, they are conducive to the enrichment and development of the theories and technologies for developing tight sandstone gas reservoirs in China, and they can be used as a reference for the development of similar gas fields.