Shale structure implication in hydraulic fracturing production results: Case study in low resistivity low quality reservoir, offshore North West Java area

Abstract

Low-resistivity & low-quality reservoir has been successfully developed in ONWJ area by using hydraulic fracturing stimulation method to optimize production gain due to low-permeability reservoir property. The purpose of this research is to understand implication of shale structure for increasing gain production after hydraulic fracturing stimulation. Implementation of hydraulic fracturing was first completed at BerylE-1 and the well could produce 455 BOPD at 560 psi in reservoir 33 and 35. This reservoir was found in Upper Cibulakan Formation that consists of various lithology’s such as very fine-grained sandstone, shale, siltstone & thin tight carbonate that deposited in shallow marine neritic to littoral environment. Production anomaly occurs after hydraulic fracturing stimulation. Some of well in this reservoir show good incremental production, but in the other well there was no significantly incremental production in this reservoir. There were three types of shale structure classification based on effective porosity distribution: laminated shale, structural shale and dispersed shale. Shale structure for each well has been defined based on Thomas Stieber plot and calibrated using petrographic analysis from 8 sample depth point. Based on this method, reservoir 33 is dominated by structural shale while reservoir 35 is dominated by laminar shale. Production data and shale type from each well has been compared and it shows that hydraulic fracturing simulation will increase effective porosity and will also increase effective permeability value. In BerylD-1 well hydraulic fracturing only completed in reservoir 35 and produced 340 BOPD with initial water cut 0 %. Laminar shale that dominates in reservoir 35 has high factor to increasing production gain after hydraulic fracturing was applied. Release of clay that caused by hydraulic fracturing will increase effective porosity and permeability.