Unlocking Depleted and Low-Modulus Telisa Sandstone Reservoir with Pillar Fracturing Technique: Well Performance Improvement Comparison with Conventional Fracturing

摘要

Kaji Semoga is an oil field located in Rimau block, South Sumatra, and currently being operated by Medco E&P Indonesia (MEPI). This field consists of three main reservoirs, namely Telisa sandstone (TLS), Baturaja limestone (BRF), and Talangakar sandstone Formation (TAF). The production from this field is mainly from BRF, which is a carbonate formation. In 1998, MEPI started to develop TLS, which is a laminated sandstone and shale reservoir at a depth of approximately 2000 to 3000 ft TVD. It has approximately 10 to 20% porosity with ranging permeability of 5 to 50 md. Telisa sandstone cannot be produced commercially without stimulation. Hydraulic fracturing is applied to increase productivity from this reservoir. Since 2002, almost 100 TLS wells have been fractured in stimulation campaign, with continuous improvement in technology and cost efficiency. The successful development of TLS with hydraulic fracturing led to further milestones to maximize oil recovery to deal with current oil price downturn. After a study with suitable samples and cases, the pillar fracturing technique was considered as a solution to increase the success ratio of hydraulic fracturing and increase the production through construction of infinite fracture conductivity. This method is similar to conventional proppant fracturing techniques where fluid and proppant are used to create conductive paths in the formation layer. However, pillar fracturing relies on open-flow channels. The proppant pillars that support the open-flow channels are created by pulsed delivery, engineered design, and innovative use of degradable fibers. With channels inside the fracture, fluid and polymer residue flow back faster than on conventional proppant fracturing, thus improving cleanup and increasing effective fracture half-length. In addition, pillar fracturing reduces the risk of screenout with the use of fibers that make fluid become more stable, while the presence of clean pulses around proppant structures promotes bridging-free flow. This paper provides a journey of the first two applications of the pillar fracturing technique in TLS, starting from candidate selection and continuing through pillar fracturing assessment and design, execution, and post-job evaluation. The technique is then compared to conventional hydraulic fracturing by reviewing initial production results from surrounding wells. Furthermore, this paper will cover how pillar fracturing could overcome conventional fracturing challenges such as early screenout, breaking to water zone, rapid production decline, and uneconomic production rate after fracturing. Two pilot wells have been safely executed with the pillar fracturing technique and the post-fracturing transient oil productivity index was superior, higher than nearby conventional fracturing wells. Another good result includes a significantly lower initial water cut in two pilot wells compared with water cut from adjacent wells. These outstanding results open the possibility for further application of the pillar fracturing technique to existing offset wells and for future production enhancement strategy.