Successful Stimulation of Sandstones in the Dulang Field, Malaysia, Using Surfactant-Based Diverter: A Novel Solution for Mature Fields

Abstract Dulang is the major oilfield in the Malay Basin. Owned by the Malaysia national oil company, Petronas, it is located in the South China Sea, about 130 km offshore the east coast of Peninsular Malaysia in water depths of about 76 m. This field, consisting of sandstone formations, was discovered in 1982 and developed fully in 1991 resulting in 48 wells being drilled and produced. Currently, the reservoirs in this field are nearly depleted, having many idle wells with high Gas Oil Ratio (GOR) and water cut (up to 95%). An attempt was made to revive the idle wells with potential recoverable reserves. A collaborative team was formed to devise a solution. The main focus was given to idle wells with high water cut. The objective was to increase oil production and reduce water cut. A number of options were reviewed, with one of the strategies being to increase oil production by shutting the water/gas production. However, due to various operational challenges that these well possess, (i.e. difficulty in mechanical isolation due to dual completion and availability of multiple water/oil zones) no direct approach could be employed. In order to keep the drive and market of idle wells afloat, a different strategy was proposed and marketed which focused on increasing the oil production with little or no water increase. The water cut in response to this strategy would be expected to be either maintained or decrease resulting in higher oil production. The introduction of matrix acidizing utilizing a high temperature viscoelastic surfactant-based diversion system has made it possible to achieve such results. A high temperature viscoelastic surfactant-based diverter was engineered to selectively plug the zone with high water saturation, allowing the treatment system to enter the zones with high oil saturation. Another advantage over the conventional particulate diverters is that it contains only a surfactant and does not have any solids or polymers. This paper discusses application and results of using high temperature viscoelastic surfactant-based technology in the Dulang fields. This paper will also cover candidate selection, pre-job laboratory testing, execution and evaluation challenges in order to properly execute the job. Candidate selection, which is the most crucial task in this project, determines the right and potential candidates for the treatment. Extensive laboratory experiments, such as crude oil and acid compatibly (emulsion and sludge tests), and core studies (SEM, XRD, core flow, etc.) have been carried out to develop the most effective acid recipe. Previous treatment results will also be discussed in this paper. The success of the treatment in Dulang has proven the potential success of the application of this high temperature viscoelastic surfactant-based diverter for selective stimulation of high water cut oil wells.