Abstract: The Bao 8 well block in Baode area is located in a complex surface zone within urban overlay areas, which imposes severe constraints on above-ground well placement. Furthermore, this well block is located in a subsurface region with complex tectonic structures, insufficient geological understanding, and significant variations in overall burial depth in the western part, which has long prevented its large-scale development. Since 2020, PetroChina Coalbed Methane Co., Ltd. has initiated large-scale hydrocarbon exploration in the surface-subsurface dual complex area of the Bao 8 well block. The "Three Integrations" development model, i.e., subsurface-surface integration, geology-engineering integration, and deployment-implementation integration, was adopted, and 100-million-cubic-meter level medium-shallow coalbed methane (CBM) platform was put in operation. Single-well investment was reduced by 7.8 %, and high-efficient development was achieved. Five key practical insights were summarized as follows:(1) In response to the complex subsurface geological conditions of the Bao 8 well block, a new round of fine structural interpretation and reservoir prediction was conducted based on comprehensively collected coal borehole data and field outcrop observations. A central sweet spot of 11.56 km² was selected as the key area for large-scale reservoir development and well deployment. (2) Guided by subsurface-surface integration and based on the updated refined structural and reservoir characterization results, differentiated well deployment was innovatively implemented in the sweet spot area. Following the principle of "horizontal wells in suitable geological formations, vertical wells in optimal reservoir zones", a hybrid well pattern consisting of one large well pad with 55 wells (35 vertical/cluster wells and 20 horizontal wells) was deployed. Through this deployment, production from high-quality reserves of 5.43×10⁸m³ and a production capacity of 1.2×10⁸m³ were achieved. (3) Under the guidance of the geology-engineering integration concept, horizontal well geosteering technology was optimized to ensure a high coal seam penetration rate of 98.6 %. Single bit-run drilling technology was applied to extend horizontal sections, with an average length of 1 006 m. Anti-collision control technology for dense well patterns on multi-well pads was adopted to ensure safe, efficient, and high-speed drilling in the Bao 8 well block. (4) To address the issues identified in previous-stage fracturing operations in the Baode area, an optimized moderate-scale fracturing technique was innovatively developed. Effective fracture volume is increased by this technique via high injection rate; fluid loss is reduced and fracture initiation efficiency is improved through application of 100-mesh sand in the pad fluid; effective propped fracture area is expanded with medium-size proppant; and fracturing costs are lowered by the use of low-cost simulated formation water. Under fluid volume control conditions, proppant volume was increased by 60 %, and the average sand ratio was doubled. (5) Through the integration of deployment and implementation, a large-platform, factory-style operation model was adopted, where simultaneous drilling was carried out by multiple rigs and zipper fracturing technology was applied, leading to a significant improvement in operational efficiency. At present, the total daily gas production of CBM wells in the Bao-8 well block has exceeded 26×10⁴m³. The average daily gas production per horizontal well is over 9×10³m³, and that per vertical/cluster well is over 3×10³m³, both of which exceed the design targets. The Bao 8 well block has demonstrated excellent gas production performance and has been recognized as a successfully developed medium-shallow CBM platform with 100-million-cubic-meter level production capacity in complex surface-subsurface areas in China.

Key words: Bao 8 well block, medium shallow coalbed methane, dual complex areas, three integrations, hundred-million-cubic-meter level production platform, development practice

摘要： 鄂尔多斯盆地东缘保德区块保8井区位于城市压覆区内的地表复杂区,地面井位部署困难。由于井区西部构造复杂、认识程度低、整体埋深变化大,一直未能实现规模开发。2020年以来,中石油煤层气有限责任公司在保8井区地表、地下双复杂区启动了规模开发工作,开展了中浅层煤层气亿立方米级大平台实施工作,采用地下—地面一体化、地质—工程一体化以及部署—实施一体化3个一体化工作模式,使单井投资降低了7.8%,实现了高效开发,并取得了5个方面的实践认识:①针对保8井区复杂地下地质条件,通过充分收集井区内的钻孔资料,结合野外地表露头的观察,开展了保8井区新一轮精细构造和储层预测研究,优选中部面积为11.56 km²的甜点区作为规模建产区,开展部署工作。②根据新一轮精细构造和储层研究成果,结合地下—地面一体化模式指导开展了甜点区差异化部署,采用"宜平则平、宜直则直"的部署原则,以混合井网的方式部署1座大井台,共计55口井(35口直丛井、20口水平井),实现了动用优质储量为25.43×10⁸m³,建设产能为1.2×10⁸m³的目标。③根据地质—工程一体化思路,通过优化水平井导向技术来保障高钻遇率,实现水平井煤层钻遇率达98.6%;通过"一趟钻"技术实现了平均水平段长达1 006 m;通过大平台密集井网防碰控制技术保障了安全钻井,实现了保8井区高效优快钻井。④针对保德区块前期压裂存在的问题,形成保8井区"大排量、前置百目砂降滤、中粒径支撑"为主、低成本模拟地层水压裂液的适度规模压裂技术;在控液条件下增砂60%,平均砂比提升1倍。⑤根据部署—实施一体化方式,采用大平台、工厂化作业模式,多台钻机同时钻进,采用拉链式压裂方式,大大提高了施工效率。目前保8井区煤层气井产气量已突破26×10⁴m³/d,水平井单井平均产气量超9×10³m³/d,直丛井单井平均产气量超3×10³m³/d,均优于方案设计,成为中国在双复杂区成功开发的中浅层煤层气亿立方米级大平台。

关键词: 保8井区, 中浅层煤层气, 双复杂区, 三个一体化, 亿立方米级大平台, 开发实践