Characterizing the Greater Burgan Field: Integration of Well-Test, Geologic, and Other Data
Authors: Kabir C.S. , Moon M.S. , Pederson J.M. , Al-Dashti Q. , Konwar L.S. , Al-Jadi I. , Al-Anzi K.G. 
Published: December 2007

Pressure transient testing happens to be a powerful reservoir characterization tool when used with geological, geophysical, petrophysical, cased-hole logs, and completion data. This work describes a multidisciplinary approach to understanding reservoir flow units in the Greater Burgan field in Kuwait. Major reservoirs in this field were deposited in a fluvial deltaic environment. As expected with this geologic setting, we encounter a wide variety of reservoir stratigraphy. These include complex discontinuous sands associated with a delta plain environment, massive distributory mouth bar/delta front sands, and open marine carbonates. Transient tests, aided by reservoir geology, helped determine depositional environments, fluid contacts, the sealing nature of faults, etc, Distributed pressure measurements contributed to our understanding of vertical flow barriers, while geochemical analyses augmented our understanding of reservoir units, both in vertical and lateral sense.

We interpreted over 400 well-tests, spanning four decades, to characterize the major layers, which are being produced separately in this giant field. We observed a variety of examples that identity channel-levee systems, gas-cap or aquifer support, layered reservoir behavior, partial-completion and dual-permeability effects, and non-sealing faults. In short, many recognizable well-test signatures were discerned, leading to much improved understanding of various flow units.

Average drainage-area pressures were estimated using the rectangular hyperbola method. Application of this robust technique became very useful because different geologic horizons and/or reservoir areas experience various degrees of pressure support.

Introduction

Pressure transient tests have long been recognized as a reservoir characterization tool. Both single- and multi-well tests have been used successfully for aiding reservoir description. Development of multitude of analytic models, advances in gauge and telemetry technology, introduction of pressure-derivative and nonlinear least-squares optimization techniques, and the use of downhole transient rate measurements, all played significant roles in understanding the reservoir architecture containing the fluids.

A large body of literature describes analytic models of various complexities that facilitate modeling reservoir flow units. Some of these models have found routine use in the industry. Although multi-well testing can potentially reveal a lot of information on areal heterogeneity, its use is rather infrequent in practice. Despite the plethora of publications, only a handful of field studies reported integration of geology with well-test interpretation in the past: Refs. 9–11 are worthy of note. Infusion of geological knowledge certainly helps reduce the uncertainty associated with any well-test interpretation. Recognizing the need for integration, research efforts are underway to use well-test data in describing the heterogeneity. Reservoir characterization is of course the first step toward modeling the fluid flow behavior.

Unlike most reservoirs, the Greater Burgan reservoirs exhibit test responses of very different character even though wells may be of close proximity. Complex depositional environment coupled with different drive mechanisms that are operative in different layers cause the transients to behave differently, reflecting the architecture of diverse flow units.

From these well-test models, besides flow-capacity, skin, and drainage-area pressure, we were able to estimate many other parameters. P. 589^