Chemical Enhanced Oil Recovery (EOR) processes are being considered for large field applications with recent high price of crude oil. However, applications are generally directed towards onshore environment, with temperature less than 85oC, using fresh water as the injection water. Malaysian oil fields are located offshore, with high reservoir temperatures of more than 100oC and use sea water as injection water. This paper reports on laboratory results that were part of an R&D project investigating the feasibility of increasing oil recovery through chemical EOR processes for oil fields in Malaysia. Chemical EOR processes investigated include surfactant, surfactant-polymer, alkaline-surfactant, and alkaline-surfactant-polymer. A unique 2-stage softening prepared seawater for the two processes using alkali. Thermal aging studies at 119oC were used to screen chemicals for stability and degradation. Interfacial tension and phase behavior tests of stable chemicals were used to select formulations. Linear corefloods and thermal degradation tests were used to select polymers. Oil recovery studies used field proportioned injected chemical volumes in radial corefloods. Dilute surfactant processes without alkali recovered little incremental oil. This was attributed to heavy consumption loss of surfactant. Average incremental oil recovery in coreflood studies by alkali-surfactant flooding was 14.6% OOIP and by alkaline-surfactant-polymer flooding was 28.6% OOIP respectively. This proved that there is potential for chemical EOR application in Malaysia. INTRODUCTION Despite the very harsh environment for chemical EOR processes in Malaysia, PETRONAS has undertaken an R&D project whose scope of work includes:Phase 1: screening of suitable reservoirs and chemical processes,Phase 2a: detailed chemical laboratory design,Phase 2b: reservoir modeling to estimate process performance,Phase 3: economic evaluation andPhase 4: conceptual pilot design. This paper focuses on the laboratory aspects of the study (Phase 2a) of the Angsi I-68 reservoir that was selected in Phase 1. It includes the overall chemical EOR processes evaluations and design, and observed incremental oil production from coreflood experiments at laboratory scale. Chemical EOR Considerations Chemical EOR processes in offshore environments are constrained much more by "footprint" or available space on platforms than are their onshore counterparts. Therefore, the simpler the process utilized the better. An ideal process would be to simply add a liquid surfactant to the seawater currently being injected. The objective would be to mobilize waterflood residual oil trapped by capillary forces by reducing interfacial tension. A single liquid surfactant would require only storage, metering, and blending into the injection stream. Any other chemicals added would have the same requirements, which may be complicated if, for instance, the chemical were a solid rather than a liquid. However, an objective of the R&D program was to investigate a range of Chemical EOR processes that may be technically viable. These included surfactant (S), surfactant-polymer (SP), alkaline-surfactant (AS), and alkaline-surfactant-polymer (ASP).

A considerable amount of hydrocarbon resource is estimated to remain in the ground even after primary and secondary recoveries in the fields.As of 2003, the estimated oil-in-place from the forty-seven producing fields in Malaysia stand at about 20.1 BSTB, with a cumulative production of 4.9 BSTB and reserves of 2.5 BSTB[1]. This translates to an averaged recovery factor of only 36.8 percent for producing fields in Malaysia.For this reason, the remaining oil-in-place of 12.7 BSTB i.e. 63.2% of STOIIP will be the prime target for Enhanced Oil Recovery (EOR) projects.On top of the value that could be gained through EOR applications, most of the fields are already entering maturing stage for primary and/or secondary depletion with declining oil rates and increasing water-cut and GOR trend. This situation will further merit the application of EOR processes.However, to date, there has been no full-field application of EOR in Malaysia, with the exception of a pilot WAG project in Dulang field[2, 3] and MEOR stimulation project in Bokor field[4–6]. In 2000, a screening study on seventy-two (72) reservoirs in Malaysia has identified almost a billion barrels of additional reserves that can be achieved through EOR.Majority of these potentials resides in a few major reservoirs, which carries about 60% of the total EOR potential7.The screening study has also identified several key EOR technologies that are most applicable in Malaysia, namely gas injection, chemical injection, and microbial.Thermal processes were investigated but have been ruled out due to the operational, properties of reservoir fluid, safety and commercial limitation of the methods for Malaysian offshore applications.However, transforming those potentials into real projects may face some challenges and change of operating philosophy.Factors such as facilities condition, sources of injection gas, reservoir characterization, technology applicability, and commercial aspects will play an important role in planning for an EOR projects in Malaysia. This paper presents the possible opportunities that could be realized by EOR applications, and discusses issues and challenges including change of mindsets required in making EOR a reality in Malaysia. Overview of Malaysian Oil and Gas History The earliest officially recorded oil find in Malaysia was made in July 1882 by the British Resident of the Baram district in Sarawak. The oil was used by the local residents for medicinal purposes and later for lighting lamps and waterproofing boats. Commercial exploitation of petroleum only began in 1910 when the Anglo-Saxon Petroleum Company, the forerunner of the present Sarawak Shell, which was granted the sole right to explore for petroleum in Sarawak, struck oil in the town of Miri, marking the start of the Malaysian petroleum industry. The Miri success encouraged further attempts to discover other onshore fields. However, only traces of petroleum were found, and these were not large enough to justify drilling activities. Consequently, by the 1950s, attention turned to the seas. This was made possible by new improvements in offshore petroleum technology. Marine seismic surveys were carried out for the first time in Sarawak in 1954. The shift offshore began to show results in 1962 with the discovery of oil in two areas offshore Sarawak. Other finds followed in rapid succession. In Peninsular Malaysia, petroleum exploration activities began in 1968 and the first oil field was discovered in 1971. As in many other developing countries, oil companies in Malaysia had been operating under what was known as a concession system. After the 1973 oil embargo, oil-producing countries of the world realize the importance of controlling their own petroleum resources.In Malaysia, it led to the promulgation of the Petroleum Development Act (PDA) in 1974 and the formation of a national oil company, PETRONAS, to ensure that the nation's petroleum resources could be developed in line with the needs and aspirations of the nation. PETRONAS, short for Petroliam Nasional Bhd, is wholly-owned by the Government, the corporation is vested with the entire oil and gas resources in Malaysia and is entrusted with the responsibility of developing and adding value to these resources.

Drilling experience in K-shale in the Malay Basin of Peninsular Malaysia highlighted the issue of wellbore stability in the formation. A wide range of drilling problems has been experienced, ranging from sloughing shale to tight hole and stuck pipe. Subsequently, a major collaborative project between CSIRO Petroleum and PETRONAS Research &Scientific Services Sdn Bhd was conducted to address the problems. The aim is to develop a technical framework of drilling fluid design and consolidate into a methodology for overcoming wellbore instability-related problems in the shale. This paper describes the outline of the project and the approach adopted in the development of the methodology. The approach is based on drilling fluid-shale interaction and proven rock mechanics principles which include an extensive laboratory testing program on downhole core specifically cut for the study. Based on the gathered drilling experience and laboratory tests conducted on downhole core material, dominant time-dependent failure mechanisms of the shale were identified. Examples of critical mud weight contour plots and design charts of pressure change (due to drilling fluid-shale interaction mechanisms) which form part of the consolidated methodology for designing optimal drilling fluid are presented. Comparisons between predicted mud weights determined from the contour plots and mud weights used in one of the fields showed an overall good agreement between the mud weights, drilling experience and hole size. Counter to operational expectations, the results from the laboratory study showed that some water-based muds, through correct fluid design, are capable of preventing time-dependent instability in the shale. The methodology provides a pragmatic approach for managing shale instability problems in drilling extended reach wells in the Malay Basin as well as other regions worldwide. The approach would result in an increase in drilling efficiency and a reduction in drilling cost. Introduction A wide range of wellbore instability-related problems has been experienced in K-shale in the Malay Basin of Peninsular Malaysia, ranging from sloughing shale to tight hole (remedied by reaming) and stuck pipe, and a range of drilling fluid designs has been implemented. The instability may be induced by either in-situ stresses that are high relative to the strength of the formation (stress-induced) or physico-chemical interactions of the drilling fluid with the shale or a combination of both1–6. The dominant instability mechanism(s) is dependent on the properties of the shale, in-situ stress environment and drilling fluid system used. One of the most effective options for solving and managing the shale instability problems concerns drilling fluid design (weight, type and chemistry). A collaborative project between CSIRO Petroleum and PETRONAS Research &Scientific Services Sdn Bhd (PRSS) was conducted to address the problems for PETRONAS Carigali Sdn Bhd (PCSB). The aim is to develop a technical framework of drilling fluid design and consolidate into a methodology for overcoming wellbore instability-related problems in the shale. This paper describes the outline of the project and the approach adopted in the development of the methodology. The approach is based on drilling fluid-shale interaction and proven rock mechanics principles which include an extensive laboratory testing program on downhole core specifically cut for the study. In addition to mechanical (stress-induced) instability mechanisms, other key drilling fluid-shale interaction mechanisms, including mud pressure penetration and chemical potential mechanisms, were included in the study.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA considerable amount of hydrocarbon resource is estimated to remain in the ground even after primary and secondary recoveries in the fields. As of 2003, the estimated oil-in-place from the forty-seven producing fields in Malaysia stand at about 20.1 BSTB, with a cumulative production of 4.9 BSTB and reserves of 2.5 BSTB 1 . This translates to an averaged recovery factor of only 36.8 percent for producing fields in Malaysia. For this reason, the remaining oil-in-place of 12.7 BSTB i.e. 63.2% of STOIIP will be the prime target for Enhanced Oil Recovery (EOR) projects. On top of the value that could be gained through EOR applications, most of the fields are already entering maturing stage for primary and/or secondary depletion with declining oil rates and increasing water-cut and GOR trend. This situation will further merit the application of EOR processes. However, to date, there has been no full-field application of EOR in Malaysia, with the exception of a pilot WAG project in Dulang field 2, 3 and MEOR stimulation project in Bokor field 4-6 .