分段压裂水平井的温度分布预测模型

Temperature Prediction Model for Multistage Fractured Horizontal Well

温度预测模型是实现基于分布式温度测试(distributed temperature sensors,DTS)解释产出剖面的基础,但定量预测低渗气藏压裂水平井温度剖面仍是一个难题。为此,建立一套考虑多种微热效应的低渗气藏压裂水平井耦合温度预测模型,模拟一口低渗气藏压裂水平井的温度剖面,分析温度剖面特征,并采用正交试验分析法评价压裂水平井温度剖面对不同因素的敏感性。研究结果表明:①压裂水平井温度剖面呈现出不规则的“锯齿状”,任一“锯齿”都对应着一条有效人工裂缝;②各级裂缝处的井筒温降基本上与裂缝半长正相关;③从趾端到跟端,各级裂缝位置处的井筒温降与裂缝半长的比值(ΔT/x f)依次递减;④压裂水平井温度剖面对各因素的敏感性依次为:裂缝半长>产量>地层渗透率>井筒半径>地层孔隙度>裂缝导流能力>水平倾角。研究成果为实现基于DTS解释压裂水平井产出剖面提供了模型基础和理论支撑,对于压裂水平井改造效果评价和出水位置定量诊断具有重要意义。

Temperature prediction model is the basis of interpreting temperature data from distributed temperature sensors(DTS)to flow profiles.However,it is still a great challenge to quantitatively predict the temperature profiles of fractured horizontal wells in low-permeability gas reservoir(LPGR).Therefore,a coupled temperature prediction model was developed by considering several subtle heat effects.The temperature profiles of a fractured horizontal well in LPGR were simulated and the characteristics of the temperature profile were analyzed.In addition,by using the orthogonal tests analysis method,the sensitivity of the temperature profile of a fractured horizontal well to different factors was evaluated.Results show that,firstly,the temperature profile present an irregular“serrate”pattern and any individual serration corresponded to an effective artificial fracture.Secondly,the wellbore temperature drops at each fracture location are positively associated with the half-length of the corresponding fracture.Thirdly,the ratio of the wellbore temperature drops to the corresponding half-length(T/x f)of each fractures decrease successively from the toe to the heel.Fourthly,the sensitivity of the wellbore temperature profile to different factors are in the descending order of:fracture half-length>production rate>permeabi-lity>wellbore radius>porosity>fracture conductivity>horizontal dip.The research results provide a model basis and a theoretical support for interpreting production profile of fractured horizontal wells based on DTS.It has great significance for the post fracturing evaluation and the quantitative diagnosis of the water-exit locations.