三维地质导向在地质工程一体化实践中的应用

Application of 3D geosteering in geology-engineering integration practice

随着非常规油气藏水平井提产、降本、增效需求的提高,地质工程一体化已经成为必不可少的勘探开发策略。非常规水平井钻井面临着来自地质和工程多方面的挑战。为了实现产能突破和效益开发,并且出于降本和提早建产的实际需求,非常规油气藏多采用水平井进行早期开发,地质上的不确定性不仅影响了水平井的钻遇率,同时增加了施工风险,降低了钻井时效。在工厂化、集约化的布井指导思想下,轨迹形态复杂的大位移三维井成为必然,进一步增加了钻井施工难度。实践证明,只有采用高效的地质导向方法,优化水平井轨迹,才能够在保证甜点钻遇率的同时,降低钻井风险,保证有效完井改造,实现效益开发。三维地质导向是建立在地质工程一体化理念上的新一代导向方法,其核心是地质导向模型重构和高精度三维地质建模,发挥"井工厂"的优势,利用水平井作为控制提高模型精度,为钻前轨迹设计优化、实钻地层预判和轨迹预调提供支撑。三维地质导向是不依赖于随钻测井工具的独立的地质导向方法,能够显著降低钻井成本,在中国页岩气和致密油水平井钻井实践中取得了良好的效果。

Geology-engineering integration has become an indispensable exploration and development strategy along with the growing demand for production enhancement, cost control and efficiency improvement of horizontal wells in unconventional oil and gas reservoirs. Unconventional horizontal wells are faced with multiple challenges in terms of geology and engineering. In order to realize productivity breakthrough and beneficial development and meet the requirements of cost reduction and productivity construction ahead of schedule, it is common to apply horizontal wells in unconventional oil and gas reservoirs for early development. The geological uncertainties impact the drilling ratio of horizontal wells, increase operation risks and decrease drilling time efficiency. According to the concept of factorylike intensive well pattern, 3D extended reach well with complex trajectory is inevitable, making drilling operation more and more difficult. Practical operation indicates that trajectory optimization of horizontal well based on efficient geosteering method is the only way to diminish drilling risks, guarantee effective completion stimulation and realize beneficial development while ensuring the drilling ratio of sweet spots. 3D geosteering is a new-generation steering method which is developed according to the concept of geology-engineering integration, and its core lies in geosteering model reconstruction and high-precision 3D geological modeling. It maximizes the advantages of ＂well factory＂ and improves the model precision by means of horizontal wells, so as to provide the support for pre-drilling trajectory optimization, drilled formation anticipation and trajectory pre-adjustment. 3D geosteering is a process independent of LWD（logging while drilling） tool. With this technique, the drilling cost is reduced significantly, and satisfactory results are achieved in the practical drilling of shale gas or tight oil horizontal wells in China.