Abstract

The Greater Burgan field of Kuwait has been producing for 57 years. The massive sandstone reservoirs have contributed the bulk of oil production. Large reserves are situated in interbedded sandstone reservoirs and will play a critical role in future Greater Burgan development. The current challenge is how to develop these reservoirs that have high uncertainty in net pay.

In the recent past, several wells were completed in the interbedded sandstone sequences and no flow was reported. As a result, a review of log, core, fluid, well tests, PLT, pressure data, and the method of net pay determination has been done. The team's objective has been to develop an integrated understanding of the net pay intervals that can contribute to flow at a given API, viscosity, depth, and reservoir pressure. It is assumed that artificial lift may be available, and that drilling, workover and completion practices do not result in any permeability or perforation damage. A conceptual model has been set up to study all the related parameters and to prove what contributes to making the well flow. Our simulation model includes vertical lift performance for the tubing size, the depth of the reservoir, and the hydrocarbon properties. The model has been calibrated using log, core, PLT and well test data.

This paper represents the details of the integrated study made to redefine net pay by improving and incorporating static and dynamic data. The objective is to guide the well completion strategy for interbedded sandstone reservoirs and reduce the uncertainty of remaining oil in place and reserves. The proposed methodology will influence future investments in infill wells, artificial lift, and improved oil recovery methods.

Background

The Greater Burgan field of Kuwait has been on production from the upper Cretaceous Wara &Burgan formations. Bulk of the production has been accounted by the generally massive Third Sand Middle and Fourth Sand members of the Burgan formation. Other reservoirs such as Wara, Third Sand Upper and Third Sand Lower members are primarily interbedded sand and shale reservoirs. These reservoirs have been deposited under various sedimentary systems typical of a delta plain environment. Some of the examples are distributory channel fills, interdistributory bays, overbank splays, bay fills, distributory mouth bars, delta front, and prodelta deposits. This diverse setting explains the complex heterogeneous nature of these reservoirs in the Greater Burgan Field.

FORMATION EVALUATION

The development of the Greater Burgan field has taken place over more than five decades; the petrophysical data demonstrate the evolution of formation evaluation tools and technology. The petrophysical data of the field consists of a wide range of different vintages and quality of data. It includes one of the first ever "electric logs". Petrophysicists have been consolidating, validating and normalizing these data to ensure reliability and consistency of formation evaluation.

Shale Volume determination

Shale volume (Vsh) has been of prime importance in developing an understanding of quality of pay. Vsh curves were calculated mainly on the basis of gamma ray (GR) and spontaneous potential (SP) data.

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