Open Hole Multistage Completion Exceeds Production Expectations from South Sulige Gas Field in China
Authors: Fan W. , Hu L. , Falxa P. , Wang Q. , Liu H. , Wong A. , Ku K.T. 
Published: March 2015

Abstract
A joint venture project in the South Sulige gas field began in 2011 with the intent of evaluating horizontal drilling and open hole multistage fracture stimulation. The South Sulige gas field has two main producing formations, both with low permeability and porosity. Like many other tight gas sandstone formations in China, fracturing is necessary in order to get economic production in pad-drilling.
To date, five wells have been stimulated with openhole multistage fracturing systems in the South Sulige field. Post-frac initial well performances are outstanding and have greatly exceeded expectations. This significant increase in production mirrors what has been accomplished using open hole multistage systems in North American unconventional reservoirs.
The use of open hole multistage completions allows the operator to customize the treatment of specific zones by isolating targeted sections with open hole packers while also allowing better production by focusing on natural fractures in the formation. By eliminating the need to run in hole casing, cementing, and perforating, completion time is greatly reduced. It can further improve operational efficiency by enabling a continuous pumping operation, and allowing for flow back immediately after the fracturing treatment to minimize induced formation damage.
This paper will discuss the overall enhanced performance achieved with staging methodology and open hole completions. The discussion will mainly focus on pre-installation wellbore preparation and operation of open hole multistage completion systems, clean-up procedures, mitigation of damage of the formation and taking advantage of natural fractures that are abundant in the South Sulige field. Open hole multi stage completions have applications in other tight formations in China where drilling and stimulation equipment availability is limited, to optimize the treatment efficiency and efficiency on the surface while maximizing production.

Introduction
The Sulige field is located in Inner Mongolia and was discovered in 2001. The depositional environment is a braided channel system with many gas pockets. The South Sulige project began in 2007 with the drilling of two exploration wells and continued into 2008 with three more exploration wells. Using the information and experience gathered in this exploration phase, development of the field started in 2011.
The South Sulige field has two main producing gas formations, Shan1 and He8. They are tight gas sandstone formations, with low overall permeability and porosity. Hydraulic fracturing is required in order to obtain meaningful production from both of these formations. Pad drilling of deviated wells has been adopted as the main production method for this field. Horizontal wells are also being drilled and produced to investigate the potential benefits.
He8 is the shallower and, typically, the better producing target. It is found at around 3,550 m deep with a thickness of approximately 15 m. It has a permeability between 0.2 and 0.4 mD and a porosity of 8%. Shan1 is found deeper, around 3,590 m and is usually stratified with thin shale layers. Typically, the permeability is around 0.15 to 0.3 mD and the porosity is similar to He8.