电缆地层测试压力梯度的计算与应用

Pressure gradient computation and application of wireline formation tester

从测试资料中计算压力梯度是电缆地层测试器的主要功能之一。压力梯度的计算方法中存在很多不确定性,经常导致计算结果存在较大偏差,因而在应用上受到限制。通过数值模拟的方法研究了储集层厚度、一定长度内有效测压点数量以及各测点压力测量误差大小分布对压力梯度计算精度的影响,结果表明:储集层越厚、一定长度内测点个数越多、各测点压力测量误差越一致,则压力梯度的计算误差越小;在测压点的选取中还需要综合考虑测压点流体性质的变化、测压点地层压力系数的变化以及各点地层连通情况等。压力梯度可应用于分析地层流体性质、确定油水界面、单井内评价储集层纵向连通性或封隔层、划分压力系统、观察流体性质的纵向变化以及辅助进行多井油藏评价等。

One function of the wireline formation tester is to calculate pressure-depth gradient llne （pressure gradient） from testing data. Its application is limited resulting from the uncertainties in the computational method which often results in a big deviation. The effect of the reservoir thickness, the effective measuring point number and the measurement error distribution of pressure-measuring points on the computational precision of pressure gradient was studied by numerical simulation. The result is： the thicker the measured reservoir and the more the measuring-polnt number and the closer the measurement errors of all measuring points are, the higher the computation precision is. The selection of measuring points should take into account fluid character, formation pressure coefficient, reservoir connectivity, etc. Pressure gradient can be applied in the analysis of the fluid character, the oil-water interface, the vertical connectivity of reservoirs, the pressure systems, the vertical change of formation fluid in single wells, and in the assistant evaluation of reservoirs in multi-wells.