Pressure analysis for horizontal wells

David Spivak, Louisiana Tech University


This study deals with the solution for pressure response of horizontal wells in three different anisotropic media: the infinite reservoir, the limited reservoir and the reservoir with constant pressure at the outer boundaries. Pressure analyses for vertical wells in various reservoirs are abundant, but there has been no comprehensive study of pressure analysis for horizontal wells in these three media.

The objectives of this work are to examine and to determine the likely effects of horizontal wells on productivity and on the integration of pressure tests.

The method of images, the concept of instantaneous sources and the Newman product method have been used. Integration of the summed source functions is achieved numerically using Simpson's rule.

All three solutions are semi-analytical and have been verified and validated. For the infinite reservoir the solution has been compared to a directional well of high angle, and long horizontal well responses have been compared to the solution for the uniform-flux vertical fracture. The solutions to the other two cases (for long horizontal wells) have been compared to published solutions for uniform-flux vertical fractures.

New equations, new pseudo-skin factors, new type curves, and new shape factors have been generated in the course of this work. The log-log type curves can be used to determine reservoir characteristics.

The influences of different well and reservoir parameters on the well productivity have been investigated and are presented to show the merits of horizontal wells. A major feature of this study is that some portions are presented here for the first time.