The analysis and interpretation of well interference effects on well performance of gas-condensate reservoirs: A case study of Arun Field (Sumatra, Indonesia)

This dissertation presents the development of the new approaches for the estimation of "per well" reserves for well in a multiwell gas reservoir system. These approaches are: (1) The formulation of gas material balance equations which allow the incorporation of withdrawal (or leakage) within the reservoir system. In this case, the "extra" withdrawal is written as an explicit relation, and is then coupled with the conventional dry gas material balance equation for the purposes of analysis and prediction. Five (5) different models are presented to account for this "leakage" (or interference)---where each of these models were developed based on observations of the performance of wells in Arun Field. (2) The development of a solution for the radial flow diffusivity equation that includes a "background pressure drop," which, of course, is tied to wells "sharing" reserves. The concept for this background pressure drop model was based on the observation that a significant number of long-term pressure transient tests performed at Arun Field showed an eventual pressure decline, rather than pressure increase or stabilization. This solution has been developed into a decline type curve model, and is used to determine formation properties and estimate gas reserves.; The concept of wells sharing reserves is not new, but the attempt to quantify reserves on a per well basis is new---and is somewhat counter to conventional thinking in reservoir engineering. Our work illustrates, as would be expected, that as a multiwell reservoir continues to be developed using infill wells, the reserves for each well "adjust" to this new configuration. Given a large-scale reservoir (such as Arun Field), we note that there is typically a "stabilization" after a particular development phase where per-well reserve estimates are of interest. Determination of per-well reserve estimates is the primary motivation for this work.; In addition to the determination of reserve estimates and formation properties on a per well basis, we have also performed an aggregate analysis for the entire production history of the Arun Field. This work presumes the entire reservoir to be "tank-like" and permits rigorous material balance analysis, as well as semi-analytical (and empirical) extrapolations of reserves.; The comparisons of results shown in this work not only validate the analysis approach, but perhaps most importantly, these results provide insight into the overall performance of Arun Field. The use of multiple techniques for the analysis and interpretation of individual well performance has been shown to be both wise and productive.