Delivering A Successful Acid Fracturing Job Through Integrated GGR Analysis and Stimulation Study, Case Study of A Tight Gas-Condensate Reservoir In Central Kalimantan, Indonesia
Authors: Rizkiaputra R. 
Published: November 2020

The biggest challenge for producing a tight (<0.1 mD) gas-condensate reservoir is its low deliverability. Therefore, it is important to consider well stimulation in the field development program. There are several types of stimulation, and one of the types which has the most impact is acid fracturing. However, thorough study needs to be carried out to ensure its compatibility with the specific reservoir condition. This paper will describe in detail how the geology, geophysics and reservoir (GGR) analysis and the stimulation study play its role to create a successful acid fracturing job in Indonesia, specifically in Central Kalimantan. The study begins with the understanding of reservoir geological concept and its characterization using multiple seismic attributes and core sedimentology. This geology and geophysical (G&G) analysis is further enhanced by performing dynamic analysis such as pressure transient analysis (PTA), rate transient analysis (RTA), and flowing material balance (FMB). Following this, feasibility of acid fracturing is assessed by performing the geomechanical analysis and acid solubility test. Moreover, the fracture geometry is also simulated to make sure the resulting fracture is able to penetrate the good reservoir quality. Then, performance projection using reservoir simulation is performed to quantify the expected incremental gain from the job. The geological concept differentiates this platform carbonate into six depositional elements, in which all of the production wells are located in the Reef Complex. It is further defined using the combination of seismic attributes, petrophysical analysis, and production performance, which are able to map the reservoir quality distribution. From the dynamic analysis, it shows that each well has massive connected gas initial in place (GIIP) with several wells are having poor facies nearby that act as the barrier. The study is followed by a stimulation study which shows that the reservoir has hard rock characteristics (Young Modulus up to 3.2 million psi) and high acid solubility (up to 95%), suitable for acid fracturing job. Simulated fracture geometry shows that it could penetrate nearby poor facies and achieve the good facies target. Then, the reservoir simulation also shows that significant production gain could be obtained from the job. Following up on the encouraging result of GGR & stimulation study, the first acid fracturing campaign in this field is sanctioned and performed safely & successfully. It delivers a very encouraging result in which one of the wells shows a productivity increase of up to 200%. Production forecast shows that post-fracturing well performance could sustain the plateau rate up to two and a half years and provide an addition of 25 BSCF of proved developed producing reserves. Material enough for increasing the field profitability and optimizing future development plans. This study shows that understanding the reservoir by doing integrated GGR analysis has significant benefit to reveal the upside potential of the field. Moreover, the excellent result on acid fracturing feasibility study and fracture design prior to the job ensures that it could be performed safely, successfully, and significantly increase the well productivity.