地质—工程—经济一体化页岩气水平井井距优化——以国家级页岩气开发示范区宁209井区为例

为了最大限度地提高资源动用率,通常都采用一次性井网整体部署的方式开发页岩气,而水平井井距设计则是页岩气井网部署的关键。在确定最优井距时,既需要掌握地质特征和钻井压裂工艺,也必须考虑气价、成本等经济因素的影响,目前国内外均没有形成较为可靠的页岩气水平井井距设计方法。为此,首次建立了一种基于地质—工程—经济一体化的页岩气水平井井距分析方法,通过地质建模、数值模拟、现金流分析3种技术手段,使用最终可采储量(EUR)、采收率和内部收益率(IRR)等3项指标对四川盆地长宁—威远国家级页岩气示范区宁209井区的页岩气开发井距进行了综合评价。研究结果表明:①宁209井区在当前的地质、工程、经济条件下,井距大于240 m可以确保页岩气平台开发的内部收益率大于8%;②井距控制在330～380 m时,可以同时兼顾单井EUR、平台采收率和经济效益。结论认为,该研究成果支撑了该井区页岩气开发技术政策的制定,为其实现页岩气规模效益开发奠定了基础。

Optimization of shale-gas horizontal well spacing based on geology–engineering–economy integration: A case study of Well block Ning 209 in the National Shale Gas Development Demonstration Area

In order to maximize the resource utilization rate, it is common to adopt one-time overall deployment of well pattern to develop shale gas, and the design of horizontal well spacing is the key to the deployment of shale gas well pattern. To determine the optimal well spacing, it is not only necessary to understand both geological characteristics and drilling fracturing technology, but also take into consideration the influences of economic factors, such as gas price and cost. At present, there is no reliable method for designing the well spacing of shale-gas horizontal wells at home and abroad. In this paper, a method for analyzing the well spacing of shale-gas horizontal wells based on the integration of geology, engineering and economy was established for the first time. Then, by means of geological modeling, numerical simulation and cash flow analysis, the well spacing of shale-gas development wells in Well block Ning 209 in Changning–Weiyuan National Shale Gas Demonstration Area in the Sichuan Basin was comprehensively evaluated by using estimated ultimate reserve (EUR), recovery factor and internal rate of return (IRR). And the following research results were obtained. First, under the current geological, engineering and economic conditions of Well block Ning 209, the IRR of shale gas platform development can be kept greater than 8% if the well spacing is larger than 240 m. Second, when the well spacing is controlled between 330 m and 380 m, single well EUR, recovery rate of the platform and economic benefit can be considered simultaneously. In conclusion, the research results support the formulation of the shale gas development technology policy of Well block Ning 209 and lay a foundation for the realization of its scale efficient development of shale gas.