基于长期边际成本的煤层气开发井型优选方法

A CBM development well type optimization method based on the long-run marginal cost

合理优选开发井型是实现煤层气经济有效开发的前提,而现有的煤层气开发井型优选方法则存在着诸多不足。为此,根据煤层气作为典型非常规天然气资源更注重单井评价的特点,从经济可行性的角度出发,构建了基于长期边际成本的煤层气开发井型优选评价方法与评价指标(EI),建立了相应的决策准则,并将该方法应用于我国两个重要煤层气盆地不同开发区块的井型优选。研究与应用结果表明:(1)在当前的技术经济条件下,沁水盆地南部A区块及鄂尔多斯盆地东缘B区块采用定向井及水平井开发均具有经济可行性,前者经济效益最佳井型为水平井,后者为定向井;(2)不同井型方案的评价结果相对于单井稳定日产气量及单井投资存在着临界值,临界值上不同井型方案的经济效益等价;(3)不同井型的EI值受气藏地质特点、单井产量剖面、煤层气市场销售价格、投资及成本等诸多因素的影响,应结合各种影响因素的变化情况,及时进行动态评价与更新,以确保决策的合理性。结论认为:该开发井型优选方法与传统评价方法相比具有内在一致性,但前者可操作性更强、评价结果更直观,能够快速、准确地优选出煤层气开发井型。

Reasonable optimization of development well type is the prerequisite to realize the economic and effective development of coalbed methane（CBM）. However, the existing CBM development well type optimization methods are disadvantageous in many aspects. CBM is a kind of typical unconventional natural gas resource, and its study focuses on single-well evaluation. In this paper, the assessment method and the evaluation index（EI） for CBM development well type optimization based on the long-run marginal cost（LRMC） were constructed on the basis of CBM characteristics from the perspective of economic feasibility. Then, the corresponding decision making criteria were established. Finally, this newly developed method was applied to the well-type optimization of different development blocks in two important CBM development basins in China. And the following research and application results were obtained. First, under the current technical and economic conditions, both directional well and horizontal well are economically feasible to the development of Block A in the Qinshui Basin and Block B in eastern margin of the Ordos Basin, and the economically optimal well type is a horizontal well in Block A and a directional well in Block B. Second, compared with single-well steady daily gas production and single-well investment, the evaluation results on the schemes of different well types present critical value, above which the economic benefit of different schemes are equivalent. Third, EI of different well types is affected by many factors, e.g. geological characteristic of gas reservoirs, single-well production profile, CBM selling price, investment and cost. Therefore, it is necessary to carry out dynamic analysis and update in time based on the change of various influential factors so as to ensure the rationality of decision-making. In conclusion, this newly developed method is intrinsically consistent with traditional evaluation methods, and it is more advantageous with strong operability, intuitive evaluation results and quick and accurate optimization of CBM development well types.