TABLE OF CONTENTS Well test analysis of a horizontal well is complex and on many occasions difficult to interpret. Before discussing the analysis procedure, it is appropriate to state the goals of the well test analysis. In general, a well test analysis of a horizontal well is conducted to meet the following objectives:
To obtain reservoir properties,
To determine whether all the drilled length of a horizontal well is also a producing length, and
To estimate mechanical skin factor or drilling and completion related damage to a horizontal well. Based upon magnitude of the damage a decision regarding well stimulation can be made.
A horizontal well test is difficult to analyze because of the following reasons:
Most horizontal well mathematical models assume that horizontal wells are perfectly horizontal and are parallel to the top and bottom boundaries of the reservoir. In general, the drilled horizontal wellbores are rarely horizontal but rather snake-like with many variations in the vertical plane along the well length. This vertical variation of a well is dependent upon tolerance used in drilling the well. Some horizontal wells, as typically shown in Figure 6-1, illustrate that a severe "snake" effect can exist along the well length. Because of this, one portion of the well may see the top reservoir boundary earlier than the remaining portion of the well, while a certain portion of the well may see the bottom reservoir boundary earlier than the remaining portion of the well. All of these variations along the well length affect a...
