This paper presents a geomechanical study on the potential of wellbore instability and sand production for a multi-field gas development in offshore Peninsular Malaysia. The objectives of the study wereto develop strategies to maintain mechanical and time-dependent stabilities of extended reach wells, andto assess sand production risk in the development wells and eliminate unnecessary downhole sand control. The data required for the study include:in-situ stresses, including magnitude and orientation, and formation pressure,mechanical and petrophysical properties of the formations transected by the wellbore, andproperties of drilling fluid and its interaction with shale formations. The likelihood of wellbore instability and sand production for the development wells was assessed using in-house developed wellbore stability and sand production prediction tools. Mud weight stability profiles showing the variation of lower and upper bound mud weights with depth were developed for typical vertical wells. Critical mud weight contour plots which show the variation of lower and upper bound mud weights with wellbore azimuth and deviation angle for preventing mechanical wellbore instability were developed for various formations. In addition, a drilling fluid design methodology that can be used for quick and reliable determination of the optimum mud design (weight, type and chemistry) was developed for the fields. Critical drawdown and critical reservoir pressure profiles for assessing sand production potential in the fields were established. Sand production was found not to be a major problem in the early stage of production. However, depletion in reservoir pressure and water-cut can significantly increase sand production risk. Introduction The multi-field development consists of four gas fields located in Malay Basin, South China Sea (Figure 1). The fields with varying volumes of gas in place are to be developed as a group to optimize development cost and achieve economy of scale. The development plan includes extended reach wells, and there is considerable concern regarding wellbore stability in drilling the wells, its effect on drilling performance and the potential for this to severely impact both schedule and budget. Furthermore, the potential risk of sand production needs to be assessed prior to completing the wells. The production experience from the nearby fields has been mixed1. An integrated geomechanics study for the multi-fields was therefore conducted to assess wellbore stability and sand production potential in the fields. The data required for the study were obtained from laboratory and field measurements. The field data from five appraisal wells (study wells) were made available for this study. Mechanical properties of the reservoir sandstones and shales were established by conducting a number of unconfined compressive strength and triaxial tests on reservoir cores. The laboratory-measured mechanical properties were then correlated with the properties derived from openhole logs. The magnitudes of the in-situ stresses and formation pressure were derived from analysis of openhole logs, standard leak-off test data, coefficient of active earth pressure and qualitative stress information relating to the in-situ stress regime. The properties of drilling fluid-shale interactions were derived based on a database estabilished for a number of drilling fluids and shales encountered in the basin in previous studies. The likelihood of wellbore instability and sand production were assessed using in-house developed wellbore stability and sand production tools.

The current topic being discussed rigorously by all oil and gas operators is declining production rates. This has caused them to put more efforts into getting the oil out of their matured reservoirs including PETRONAS. One of the initiatives by PETRONAS recently was to undergo a short term production enhancement project. There were various recommendations and opportunities evaluated. Among them is the Low Pressure System, which was chosen due to its simplicity and mobility. The Low Pressure System or LPS in short, is a system that utilises the well test unloading concept, using the common well testing equipment package. It is relatively easy to assemble and is not a permanent structure and can be mobilised from one platform to another. The sizing of the equipment can be customised based on the deck space availability as well as the reservoir potential. Well candidates for the system are those with low tubing head pressure and flowing with biggest choke size as these wells are unable to flow due to the back pressure effect from the export pipeline. To date, two fields were tested and the gains were more than initially expected. One of the fields has had all of its idle wells flowing and producing more than 500bopd. This paper will share how the wells were selected, the results and challenges during the implementation of LPS. Introduction Across the world, production has gone pass peak oil. Clearly, the days of easy oil have long gone. With soaring demand and depleting reserves, every oil company in the world is scrambling to maximise their production. With matured oil fields, many wells are no longer producing i.e. idle or producing with very little oil. Not so much due to depleted reserves, but due to declining reservoir pressure. In Malaysia, this is no exception as it is estimated that more than 60% of the producing fields have been producing for more than 30 years. Therefore, continuous efforts are needed to ensure the production from these fields is maximised and optimum amount of recoverable oil is being extracted from these matured reservoirs. One of the many initiatives to optimise field reserves recovery that was introduced by PETRONAS recently was the Short Term Production Enhancement (STPE) Project. The project involved ten matured fields and the study period took two months to complete. It studied all the short term opportunities that can be implemented in the matured fields within the next 6 months.. Various opportunities were evaluated and several recommendations were considered and implemented as a result from the STPE study. One of them is the Low Pressure System, which was chosen for implementation due to two characteristics; simplicity and mobility. The Low Pressure System or LPS in short, is a system that utilises the well test unloading concept, using common well testing equipment package. The uniqueness of LPS is that it utilises old technology but repackaged as a new solution. What is LPS? Low Pressure System or LPS for short is an innovative total solution aimed at enhancing field production within a short time cycle. LPS is a unique integrated subsurface and surface approach encompasses engineering study, system design and system operation as shown in Fig. 1.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper presents a geomechanical study on the potential of wellbore instability and sand production for a multi-field gas development in offshore Peninsular Malaysia. The objectives of the study were 1) to develop strategies to maintain mechanical and time-dependent stabilities of extended reach wells, and 2) to assess sand production risk in the development wells and eliminate unnecessary downhole sand control. The data required for the study include: 1) in-situ stresses, including magnitude and orientation, and formation pressure, 2) mechanical and petrophysical properties of the formations transected by the wellbore, and 3) properties of drilling fluid and its interaction with shale formations. The likelihood of wellbore instability and sand production for the development wells was assessed using in-house developed wellbore stability and sand production prediction tools.Mud weight stability profiles showing the variation of lower and upper bound mud weights with depth were developed for typical vertical wells. Critical mud weight contour plots which show the variation of lower and upper bound mud weights with wellbore azimuth and deviation angle for preventing mechanical wellbore instability were developed for various formations. In addition, a drilling fluid design methodology that can be used for quick and reliable determination of the optimum mud design (weight, type and chemistry) was developed for the fields.Critical drawdown and critical reservoir pressure profiles for assessing sand production potential in the fields were established. Sand production was found not to be a major problem in the early stage of production. However, depletion in reservoir pressure and water-cut can significantly increase sand production risk. Mechanisms for Wellbore instability and Sand Production Wellbore Stability.There is a range of factors that can affect stability of wellbores, particularly in shales. The factors include wellbore profile, properties/characteristics of the shale, in-situ stress and formation pressure, and properties of the drilling fluid. In

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