Successful Implementation of Horizontal Multi-Stage Fracturing Enhanced Gas Production in Heterogeneous & Tight Gas-Condensate Reservoirs: Case Studies

Abstract

Heterogeneity and tightness of carbonate retrograde reservoirs are the main challenges to maintain gas well productivities. The degree of heterogeneity changes over the field and within well drainage areas where permeability decreases from few millidarcies to less than 0.2 md. Thorough studies have been conducted to exploit these tight reservoirs and not only focused on well performance, but have extended to assure enhancing and sustaining gas productivity through practical applications of technologies. The main objective of this paper is to assess the performance of Multi-Stage Fracturing (MSF) in horizontal wells that were drilled conventionally and did not meet gas deliverability expectation. This paper gives a detailed analysis of well performances, exploitation approaches, and successful implementation and optimal cases to utilize new completion technologies such as horizontal multi stage fracturing to revive low producing gas wells due to reservoir tightness. Placing the horizontal wellbore reference to the stress directions plays a major role in the success and effectiveness of fracturing in enhancing and sustaining productivity. Several wells have been drilled in tight reservoirs, but could not achieve or sustain the target gas rate. Recently, two wells were geometrically sidetracked targeting the development intervals based on logs of the original hole and completed with MSF toward the minimum stress direction. Open hole logs showed a low porosity development similar of the vertical holes. However, after conducting multiple stages fracturing, both wells produced a sustainable rate of more than 25 MMSCFD that prompted to connecting them to gas plants. Placing these sidetracks in the minimum stress direction helped to create transverse fractures that connect to sweet spots and sustain gas production. This paper provides thorough guidelines for selecting optimal candidates for MSF based on reservoir heterogeneity, proper design and execution of fracturing. It also addresses various components that contributed to the success of both wells, such as reservoir development, workover preplanning, geo-mechanics studies, drilling operations and real-time support, completion operations optimization and best-practices, and performance evaluation of other producers in the field. The paper also includes essential recommendations for development of tight gas reservoirs.

SVM modeling of the constant volume depletion (CVD) behavior of gas condensate reservoirs

“…Therefore, a reliable prediction of the performance of gas condensate reservoir during pressure depletion is necessary in evaluating new fields and determining their reserve Boom et al, 1996;Morel et al, 1997;Olaberinjo et al, 2006). Lack of sufficient knowledge about gas condensate reservoirs not only leaves huge amounts of precious condensates in the reservoir but also severely damages the well productivity and lowers the gas deliverability through formation of condensate in the reservoir, especially in near well bore areas (Al-Anazi et al, 2012;Barnum et al,1995). Condensate blockage is caused by isothermal condensation of heaver components in the gas due to pressure drop caused by production and may reduce the gas relative permeability up to 70%e95%.…”