基于灰色关联的大牛地气田水平井产能评价方法

A method based on grey correlation to evaluate the productivity of horizontal wells,Daniudi gasfield,Ordos Basin

气田开发过程中的产能评价是衡量气田开发效果的重要指标。为了充分认识气田开发过程中水平井生产能力、建立合理的产能评价方法,以鄂尔多斯盆地大牛地气田为研究对象,对工区范围内9口水平井的地质、开发数据建立样本库,重点从地质认识和压裂施工两个环节分析了水平井产能影响的主控因素,筛选了气层垂深、水平段长、砂岩长度、砂岩钻遇率、显示长度、显示钻遇率、平均全烃含量、最大全烃含量、孔隙度、渗透率、含气饱和度、气层厚度、压裂段数、总液量、总加砂量、单段液量、单段加砂量等17项因素建立产能评价表征模型,应用灰色关联算法对各影响因素进行优选,最终建立QI值与无阻流量的映射关系式,并实现了水平井产能的快速评价。研究结果表明,大牛地气田实钻井实测无阻流量值与产能评价方程计算所得无阻流量值相差较小,相对误差在10%以内。结论认为,新的产能评价方程可以很好地满足现场实际应用,为该气田水平井的钻井和压裂改造效果的预测提供了指导,为该气田长期稳产30×108 m^(3)/a提供了理论支持。

Productivity is an important index to evaluate the development effect.In order to sufficiently make clear the production capacity of horizontal wells in the process of gasfield development and establish a reasonable method for evalu⁃ating the productivity,9 horizontal wells in Daniudi gasfield of Ordos Basin were taken as objectives to create a sample da⁃tabase containing geological and development data.Then,the main factors influencing the productivity were figured out from two aspects of both geological cognition and fracturing operation,and 17 factors were screened out to establish a pro⁃ductivity evaluation and characterization model,including vertical depth of gas reservoir,length of horizontal section,sand⁃stone length,drilling rate of sandstone,show length,show drilling rate,average total hydrocarbon,maximum total hydrocar⁃bon,porosity,permeability,gas saturation,thickness of gas reservoir,number of fracturing stages,total liquid volume,total sanding volume,single-stage liquid volume,and single-stage sanding volume.In addition,these factors were optimized by means of a grey-correlation algorithm.Finally,after establishing one mapping relational equation between QI value and ab⁃solute open flow(AOF),the productivity was evaluated quickly.Result shows that the real AOF in Daniudi gasfield is less deviated from the value from the productivity evaluation equation,less than 10%of relative error.In conclusion,the new equation can not only satisfy the field application very well,but also provide the guidance for horizontal-well drilling,and the prediction of fracturing effect,and the theoretical support for the long-term stable production of 3 billion cubic meters in this field.