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. results Five wells were successfully stimulated in the Dulang field using this new diversion technique resulting in oil gain ranges from 100 - 300 bopd per well (originally the wells were in idle conditions).In many cases, the wells were producing 90% water before shut-in and now producing around 80% after the stimulation treatment. A comparison of oil and water production, pre and post job is presented. The field results from the use of this system clearly demonstrate the effectiveness of the technology in selective oil zone stimulation in oil-water sections. Introduction The Dulang Unit Area (Map 1) covers the central part of highly heterogeneous Dulang Field which is located offshore Peninsular Malaysia. The Unit Area consists of a 19-stacked shaly sandstone reservoir that are divided into approximately 90 fault blocks containing multiple fluid contacts. The estimated Original-Oil-In-Place (OOIP) is around 700 million stock tank barrels (MMSTB). The crude gravity averages about 39 deg API. The associated gas production is about 45 million standard cubic feet per day and it contains more than 50% CO2. The E group of sands includes E10/11, E12/13, and E14 reservoirs and is one of three most significant groups in terms of reserves.

fax 01-972-952-9435. AbstractWhether a cement -squeeze operation results in an annular seal depends heavily on how far the cement can penetrate and disperse in the fine channels of a partially cemented annulus. In many cases, conventional or microf ine cement slurry will dehydrate and bridge off before it can achieve its objectives. This paper describes the use of engineered, optimized slurry for a squeeze operation in the Duyong B-4 well, which had a perforated zone that demonstrated a low rate of seawater injectivity. This paper also presents the slurry design and properties, execution procedure, and prejob and post-job log evaluations.After several years of production, gas bubbles appeared in various locations throughout the Duyong field. Shallow seismic showed gas charging in several shallow gas layers throughout the Duyong field. Several wells were investigated as possible contributors to the charging of the shallow sandstone layers, and Duyong B-4 was selected as a probable contributor. Duyong B-4 is a gas well completed in November 1983 with four producing zones. In September 2003, this well was selected as a test well to evaluate the cement quality behind the casing. Both cement bond logs and ultrasonic imaging logs showed gas and fluid channels behind the casing. An optimized cement slurry (OCS) was engineered and tested in the laboratory under the well conditions. Results showed excellent penetration in narrow gaps, optimum fluid-loss control, and low rheology, both at surface and downhole con ditions.The slurry was used in the squeeze operation; post -job logs demonstrated the success of the treatment. The slurry penetrated the narrow gaps without dehydrating, and good mechanical properties were achieved in short setting times.These properties are especially important in gas -producing wells and they met all the objectives set forth by the client. *

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Summary Whether a cement-squeeze operation results in an annular seal depends heavily on how far the cement can penetrate and disperse in the fine channels of a partially cemented annulus. In many cases, a conventional- or microfine-cement slurry will dehydrate and bridge off before it can achieve its objectives (Nelson et al. 1990). This paper describes the use of an engineered, optimized slurry for a squeeze operation in the Duyong B-4 well, which had a perforated zone that demonstrated a low rate of seawater injectivity. This paper also presents the slurry design and properties, execution procedure, and prejob and post-job log evaluations. After several years of production, gas bubbles appeared in various locations throughout the Duyong field. Shallow seismic readings showed gas charging in several shallow gas layers throughout the Duyong field. Several wells were investigated as possible contributors to the charging of the shallow sandstone layers, and Duyong B-4 was selected as a probable contributor. Duyong B-4 is a gas well that was completed in November 1983 with four producing zones. In September 2003, this well was selected as a test well to evaluate the cement quality behind the casing. Both cement-bond logs and ultrasonic-imaging logs showed gas and fluid channels behind the casing. An optimized cement slurry (OCS) was engineered and tested in the laboratory under well conditions. Results showed excellent penetration in narrow gaps, optimum fluid-loss control, and low rheology, both at surface and downhole conditions. The slurry was used in the squeeze operation; post-job logs demonstrated the success of the treatment. The slurry penetrated the narrow gaps without dehydrating, and good mechanical properties were achieved in short setting times (Moulin et al. 1997). These properties are especially important in gas-producing wells, and they met all the objectives set forth by the client. Introduction The Duyong gas field is located offshore, approximately 220 km (136 mi) east of peninsular Malaysia. The first gas from the field was produced in 1984. The complex comprises three wellhead platforms (DDP A, DDP-B, and DDP-C), a central processing platform (CPP), a gas-compression platform (GCP), a flare tripod (FT), and a living-quarters platform (LQP). The platforms that make up the main complex—the LQP, CPP, GCP, and DDP-B platform—are connected by a bridge. The FT is located north of the CPP and is connected by a bridge to the CPP. DDP-A and DDP-C are remote to the CPP complex. Each wellhead platform has nine well slots. Four wells were completed on DDP-A, six wells on DDP-C, and six wells on DDP-B. The fluids from the wells are piped to the CPP. Separation of gas condensate and produced water, dehydration of the gas, and metering and disposal of the produced water take place at the CPP. Gas is then piped to shore through the peninsular Malaysia gas system. The Duyong shallow-gas second-mitigation studies indicated that Well B-4 had fair-to-poor cement bond behind the 9??-in. casing. There are no data on the cement quality behind the 13?-in. casing. Furthermore, casing to casing pressure was observed in the annuli of CCP1 between the 9?? and 13?-in. casing and in the annuli of CCP2 between the 13?- and 20-in. casing. The observed pressures are believed to originate from gas channeling behind the casing(s).

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