This paper presents a case study of the first horizontal well in ADX field, Malay basin, which was drilled with an objective of maximising oil production from one of the minor reservoirs. In longer term, this well will be used as water injector once the reservoir pressure has been depleted, as part of the pressure management strategy in the field. To optimise the current production and the sweep efficiency at a later stage, a minimum of 500-m lateral length was planned for this well.The target reservoir contains gas cap without any aquifer and is currently produced with natural depletion. The plan was to place the horizontal well as close as possible to the base of the sand and as far as possible from the known Gas-Oil-Contact, to delay gas breakthrough and to use it as water injector at a later stage. An upper TVD limit was determined in which the wellbore should avoid to keep certain distance from the gas cap. However, the formation in the target location was expected to have a dipping-up trend, which could significantly limit the vertical space to steer the lateral section and achieve the minimum target length.A full suite logging-while-drilling measurement including deep directional resistivity which enabled 3D detection of approaching boundaries; combined with a proactive well placement method executed by collaborative experts from multidiscipline teams were used to address these challenges. As a result, the horizontal well was placed accurately within 0.5 m from the base of the reservoir along a 500-m lateral section; achieved with 3D geosteering decisions to avoid both the base and the upper TVD limit. Following the success of this first horizontal well in the field, another horizontal water injector well targeting a very thin reservoir was drilled successfully in the same field by applying similar methods and processes.
The paper covers the application of new technology drilling and completions equipment in horizontal wells to maximize production and recovery in a thin oil rim reservoir. The parallel process applied to the engineering design, drilling and completion operations, real-time decisions, and results are presented. As part of the second stage development of a mature oil field offshore Malaysia, a shallow target was identified. Initial engineering and reservoir studies suggested that three deviated wells or two horizontal wells would be required to develop the area. While the horizontal wells option was expected to have lower costs, the well construction was far more technically challenging. To ensure maximum production and recovery a 2,000ft lateral section was required, further detailed studies indicated that for the long lateral to be successful, well placement with respect to reservoir boundaries and fluid contacts, and open-hole sand screens of a high mechanical integrity would be critical. Additionally, in order to ensure even oil production and limit early water and gas production In-flow Control Devices (ICD) would be required as part of the completion. The well was actively steered using a Rotary Steerable System (RSS), and Logging While Drilling (LWD) measurements including a deep azimuthal resistivity distance to boundary device. Drilling was very efficient with the well placed close to the top of the sand, avoiding shale contact that could cause screen plugging, and the required distance from fluid contacts. The Real-Time (RT) logs were used to select optimum settings for the adjustable ICD completion prior to running in hole. The completion was run without incident and when the well was placed on line, produced without water breakthrough and without requiring gas lift due to effective clean-up of the entire horizontal section. Production from the well has exceeded expectations and is currently over double that of traditional wells. The application of advanced well placement technology and field adjustable ICD completions has enabled the economic development a small area of remaining hydrocarbon in a mature field, while maximizing production and recoverable reserves. Even with the increased technology cost, the overall project cost was 15% less than if standard well construction techniques had been applied. The accurate placement of the wellbore close to the upper shale and even production along the lateral due to the ICD completion has resulted in a more efficient reservoir sweep increasing recoverable reserves by ~100 MSTB.
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