Black Gold From An Old Field: Redefining Methods To Revive Hydraulic Fracturing As An Effective Stimulation For Sangasanga's Tight Oil Potential

Abstract

Generally, East Kalimantan reservoirs consist of deltaic sand bodies deposited as lenses with high heterogeneities. As the tight formations of these reservoirs are often uneconomical, some are left undeveloped due to the necessity of stimulation job. In addition, operators are typically faced withnumerous operational and technical challenges such as thin layer reservoirs, weak shale barriers, coal streaks, high pour-point oil, and over-pressure zones. Over the past decade, few major oil companies in this region have performed frac operations, with less than 10 wells fracced per year with varying and unpredictable results.

Afterall, Sangasanga still has remaining reserves for further development. Fracturing efforts in this field are intended either to expedite production or proving up reserve. Over the last 8 years, 25 frac operations have been performed in more than 10 different formations. With limited data and low reservoir uniformity, statistical analysis is challenging as there are little to no trends in the key parameters. As a result, fracturing success ratio dropped from 70% to 30%, mainly because of inaccuracy and inconsistency between the predicted and actual results.

A detailed review of previous fracturing design and execution was conducted to revise the fracturingapproach workflow. The main sequences are data normalization and applying unique coefficient of key parameters. Trial and error approach is used to match the coefficient against the production outcome. The results are then summarized in a simple yet conclusive graph. In addition, several key factors and cut-off values to consider when selecting fracturing candidates were identified. DFIT campaigns were also performed to gather data to help predict the fracturing outcome and plan for the operational resources required for execution.