The offshore Angsi Field has productive oil and gas horizons extending from 5000 to 9000 feet TVD. The tight “K-Sand” interval has a permeability ranging from 0.01 to 3 md. Even in this tight gas formation, the fracture conductivity was shown to be a controlling factor in productivity, with a 400% production increase achieved with the high conductivity fractures.
The first known multi-stage hydraulic fracture stimulation of a well utilizing equipment completely self-contained on a floating drilling rig was successfully performed in the Angsi field approximately 170 km off the east coast of Peninsular Malaysia. Three low permeability gas sands were fractured on Esso's Angsi-4 appraisal well to obtain quantitative productivity improvement data required for development planning.
Four multi-stage frac treatments of 37,000 pounds of proppant in approximately 14,000 gallons of fluid were pumped from the deck of the semi submersible rig Hunter utilizing a batch mixing configuration. Overall results of the fracture stimulations were very positive, yielding a fourfold increase in productivity over pre-frac production rates. While well performance was better than anticipated, several technical, logistical and "first time" operational challenges were confronted. Through detailed planning, equipment modification, and enhanced operating procedures, these challenges were overcome.
Relatively small propped fracture stimulations performed during exploration/appraisal from a floating drilling rig are a technically viable and economic way to obtain critical information required to fully evaluate marginal or uncertain development scenarios in the presence of tight reservoirs. This case study focuses on the operational aspects of the frac jobs while emphasizing technical and operational planning, execution and limitations experienced.
Author(s): D. A. Frye, Esso Production Malaysia Inc.
Paper Number: SPE 36402