Abstract

The main source for formation damage measurement is transient well testing. The formation damage measured is referred to as the skin factor. To reduce cost and operational risk, many wells are tested with surface shut-in and bottomhole pressure measurement. If properly designed, performed, and interpreted, these tests provide valuable information on the well's skin condition.

Wellbore storage becomes a very important factor with a surface shut-in. In addition to the wellbore fluids' compression and phase changes, temperature effects may be significant and extended depending on many factors including the well's depth. However, field data has shown that available analytical models do not accurately predict wellbore storage duration and pressure behavior. Moreover, extended wellbore storage pressure data may appear to behave in a way similar to radial flow as seen on the pressure derivative curve. This misinterpretation usually results in a negative skin and the creation of nearby boundaries (i.e. which results in smaller reservoirs) making high potential wells appear to be limited.

This paper will present empirical and practical field solutions to this problem. Well test, stimulation, and production field data supported by computer simulations from oil and gas wells in the Gulf of Mexico area will be presented. The data presented in this paper will demonstrate how the test design and interpretation will effect the overall reservoir and well management of the field.

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