Abstract

The West Asset of Brunei Shell Petroleum (BSP) is an offshore-based oil & gas production asset with substantial volumes of non-associated gas from deep, low permeability reservoirs. The typical depths of these reservoirs are from ca. 9000 ft to 11000 ft tvdss having a permeability range of 0.1 - 10 mD and porosity range of 9% -13%.

In the past, the completion type for the deep, tight gas reservoirs has been primarily cased-hole and perforated. The production rates has not been sustainable and was observed to decline faster than expected and ceased production, at reservoir pressures significantly higher than expected abandonment pressure. Investigation showed that these wells quit prematurely due to high skin, although the actual damage mechanism i.e. from fines migration, condensate banking, water banking or clay swelling, is still unknown. Production remediation via acid stimulation and through-tubing re-perforation did not achieve the desired results.

Consequently, there is a demand for the West Asset to pursue different completion strategies primarily dedicated to develop deep, tight gas reservoirs. Hydraulic fracturing is one of the completion concepts proposed to test the reservoir producibility performance. Other than a failed "Skin-Frac" campaign attempt in the past, hydraulic fracturing technology has not been widely applied in BSP. With a lack of geomechanics data and fracturing experience, a number of challenges were confronted during well planning and completion design phase as well as during planning and execution of the hydraulic fracturing campaign.

In the past two years, two wells have been hydraulically fractured by bull heading through 4-1/2" monobore completion via frac boat. Therefore, this case study documents the evolvement of completion and hydraulic fracturing strategies, emphasizing the importance of perforation selection, fluid selection and hydraulic fracture designs to the overall outcome of well performance. This paper also captures the operational challenges and learnings experienced throughout the campaign. This campaign has gathered valuable information on fracturing data and provided better understanding on future completion and fracturing approaches for new tight gas wells in the West Asset and similar assets in Brunei.

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