水敏性泥页岩地层孔隙压力预测方法研究

The Research of Predicting Pore Pressure in Clay Shale Formation with Water Sensitivity

基于平衡压实理论的等效深度法、Eaton法是砂泥岩地层孔隙压力预测最为常用的方法之一,基于声波、密度、电阻率等测井曲线合理构建正常压实趋势线则是该类方法可靠、准确的基础与关键。但对水敏性泥岩而言,由于与水基钻井液长时间接触产生强烈的水化作用,导致测井数据不能准确反映地层的真实压实状况,从而导致地层孔隙压力测井预测难度大、精度低。鉴于此,在泥页岩组分特征测试分析基础上,实验研究了钻井液作用下水化对泥岩声波时差、电阻率以及密度的影响,进而建立了泥岩去水化方法及考虑水敏性泥岩水化作用的正常压实趋势构建方法,形成了适用于水敏性泥岩地层孔隙压力的预测方法。应用该方法对北部湾某区块部分井进行预测,与实测值吻合程度较好,具有实用性。

The common methods of predicting pore pressure in clay shale formation are Eaton and equivalent depth method,which are based on DT,GR and CAL datum to establish the trend line of normal compaction. But because of strong hydration swelling ability of clay shale,log data is not precise. So it is difficult to predict its pore pressure. Base on the above theories and the analysis of rock component,experiments were conducted to analyze the effect of hydration on rock＇s Acoustic time,density and electricity resistivity. By doing those work,the effect of hydration was eliminated and trend line of normal compaction without hydration effect was established,which are formed a method of predicting pressure in clay shale formation. By this method,a few wells in Beibu gulf basin were predicted. The result is good and indicates that the method is practical.