Field Test of SAGD as Follow-Up Process to CSS in Liaohe Oil Field of China
Authors: Yang L. 
Published: March 2010

Abstract
The Du 84 block of the Shu-1 area in the Liaohe Oil Field is located in Panjin City, Liaoning Province, China. The production formation, Guantao, contains extra heavy oil with a depth of 530–640 m. The reservoir is characterized in thick pay, with high permeability and a very active aquifer. The dead oil viscosity is 230,000 mPa.s at 50 °C.
Although the Cyclic Steam Stimulation (CSS) process using vertical wells has been applied successfully in producing oil from the reservoir, the anticipated ultimate oil recovery is less than 29% of the original oil in place (OOIP). To enhance oil recovery beyond that of the CSS, physical and numerical modeling studies were carried out. The Steam Assisted Gravity Drainage (SAGD) process using a combination of vertical and horizontal wells was proposed as a follow-up process to CSS. An additional 27% recovery is anticipated with the proposed follow-up process. This would give a total recovery of 56%.
A pilot with four horizontal producers was implemented in the field. CSS was used initially in the horizontal wells for establishing the communication with the surrounding vertical wells. The pilot was then converted successfully to SAGD operations with horizontal wells as continuous producers and some of the surrounding vertical wells as continuous injectors. A total of 44,500 m3 of oil has been produced over the 12 months of SAGD operations between June 2005 and June 2006. The field implementation process and pilot performance, as well as the challenges with this project, are presented in this paper.

Introduction
This paper is the continuation of an earlier work(1) in which a field pilot was proposed for testing Steam Assisted Gravity Drainage (SAGD) as a follow-up process to CSS based on a reservoir model and feasibility studies. Two field pilot projects were constructed in 2003 in the Du 84 block of the Su-1 area in the Liaohe Oil Field. One pilot is producing from the Xinglongtai formation and the other one is producing from the Guantao formation. The pilot in the Guantao formation was converted to SAGD operations in early 2005 and the field results are encouraging. The field performance from this pilot is reported in this paper.
The Steam Assisted Gravity Drainage (SAGD) process, which was described by Dr. R.M. Butler in the late 1970's(2), has been applied successfully for the production of bitumen and heavy oil since it was tested in the Underground Test Facility (UTF) in the Athabasca oil sands of Alberta, Canada(3). Several commercial projects have been implemented in the field in Canada since then. The Liaohe Oilfield Company constructed its first SAGD pilot in China in 1996 in the Xinlongtai formation, which contains extra heavy oil at a depth of 750 m from the surface. The pilot consisted of one stacked well pair and was operated for about one and a half years. The suspension of the pilot test was due to:insufficient lift capacity provided by the gas lift system; and,difficulties in communication resulting from too large a vertical separation between the injector and the producer.