水平坑井における圧力解析の実例

Abstract

Although quite a few horizontal wells have been drilled in the world, a pressure interpretation using actual pressure data and production profile has been rarely reported. An example of practical pressure interpretation by the Automated Pressure Analysis System developed by authors, together with the prediction results of future production performance by a reservoir model matched with the actual pressure data are presented in this paper.There are several problems for pressure interpretation of a horizontal well. Firstly, the early time pressure data, which is important to estimate KV/KH, are often masked by a, wellbore storage effect. Secondly, when reservoir permeability is low, it takes too long a time for the pressure behavior to reach a pseudo radial flow condition for which the traditional pressure interpretation methods can be applied. Thirdly, due to the rapid change of a flow regime, it is difficult to keep the production rate of a horizontal well stable in the early production stages, as a result, currently available interpretation methods cannot properly anslyze the results.In order to solve the above mentioned problems, we have developed the Automated Pressure Analysis System which can automatically determine four reservoir parameters, i.e. Horizontal Permeability (KH), Vertical-Horizontal Permeability Ratio (KV/KH), Skin Factor (S) and Wellbore Storage Coefficient (CD) from the pressure data, even when the production rate is unstable.On the other hand, pressure matching using a reservoir simulator was conducted and its result was compared with the one by the Automated Pressure Analysis System. The reliability of the Automated Pressure Analysis System was confirmed by comparing the above result independently.