Formation Damage in Gravel Packed and Non-Gravel Packed Completions: A Comprehensive Case Study

Abstract

ABSTRACT A comprehensive formation damage study was undertaken on selected fields in the Baram Delta acreage, offshore East Malaysia, to determine the extent and main causes of formation damage in the area. This was due to the high skin factor values interpreted from most transient well tests conducted throughout the years. A total of 70 gravel packed and 60 non-gravel packed wells (involving 220 completion zones) in 6 fields were covered in the study. Based on statistical and pressure transient data analysis as well as an in-depth review of drilling and completion activities, it was found that the majority of non-gravel packed wells have low or negligible formation damage. Between 60 and 70% of the non-gravel packed wells have skin factors of less than 10. Most of these wells have constant skin factors as a function of time indicating that the damage, if any, did not increase with oil production. On the other hand, the majority of gravel packed wells were damaged. As much as 70% of these wells have skin factors varying between 10 and 40. About half of these gravel packed wells have skin factors which increased with time indicating that the damage worsened with oil production. Formation damage in these gravel packed wells may be attributed to the gravel packing operations. This was further substantiated by well test results which showed that skin factors immediately after perforating were essentially zero while those determined from pressure build-up tests carried out at a later date after gravel packing operations were in the order of 10 to 100. It was also observed that although improvements in gravel packing and perforating practices were implemented through the years, no significant enhancement of flow efficiencies had resulted.