Multistage Fracturing in Horizontal Open Hole Completions: Case Studies for Low Permeability Fomations in China
Authors: Hill Eric Stanley William , Jiang Xiaoming , Lin Yongxiang , Li Wenquan , Wang Guoyong 
Published: May 2016

Horizontal completion technology has progressed dramatically over the past decade with the latest single trip ball actuated sliding sleeve fracturing technology becoming widely accepted by the oil and gas industry. These horizontal completions have allowed multiple zones to be fractured and then produced very quickly compared to standard conventional methods.

This completion technique isolates and allows specific placement of fracture stimulation treatments at multiple desired intervals along the well. Operational efficiencies have been realized by eliminating cementing, perforating, and by improving stimulation operation efficiency by pumping all fracturing treatments successively (Miller et. al. 2008, Hlidek et al. 2011, Johnson et. al. 2010).

Rising natural gas consumption in China coupled with higher depletion rates of new and existing reserves are creating increasing demand. This demand has driven the need to increase exploration and development of low permeability fields.

With continued development in these low permeability formations around the world, horizontal wells with continuous stage fracture stimulations have become increasingly used for both unconventional and tight formation reservoirs. Case studies involving four areas of China with a total run history of 79 wells will be examined. These areas include Daqing in Northeast China, Sulige in the Northwest Ordos basin, Sichuan basin, and a tight oilfield in Shandong province. Each field has had separate independent challenges including H2S gas, CO2 gas, reservoir heterogeneity, low and ultra low permeability, low reservoir pressures, and high fracture gradients. Both propped fracture treatments and acid fracture treatments have been executed with the system and the applications will be discussed.

This paper will focus on planning and execution strategies followed by application on different types of formations and lessons learned from applications in China. Furthermore, production data will be compared with other well completion strategies currently employed in these fields. New features to improve operational efficiency and future system improvements will also be presented.

Background

The single-trip multizone openhole fracturing completion system has proven to be an effective well completion technique and is well suited to low permeability reservoirs. It uses specially designed openhole packers and ball actuated fracturing sleeves to isolate intervals of a horizontal section for selective fracture treatment placement throughout the horizontal wellbore. The fracturing sleeves are opened by dropping balls between fracturing stages of the fracture treatment program. As the ball reaches the sleeve, it shifts open and exposes a new section of the lateral wellbore and isolates the previously finished fracture treatment. This method provides improved control of the treatment placement throughout the openhole by isolating all individual fracture treatments in the wellbore. This allows the operator a more effective well stimulation and improved productivity (Miller et. al. 2008, Hlidek et al. 2011, Johnson et. al. 2010).