The Kutai Basin, has been under production for more than 40 years and many wells have been drilled to develop the area. This has resulted in reservoir-induced drilling problems, like kicks and lost circulation due to depletion, while some high-pressure zones still exist. This complexity makes pore-pressure and stress analysis difficult. To address this problem, a comprehensive reservoir-evaluation program was developed by adding formation pressure testing to the planned quad-combo logging-while-drilling (LWD) program. Pressure measurements in this development stage were planned to aid the operator's understanding of the field's current hydraulic communication pathways, to relate reservoir characterization to the geological model. Emphasis was on the insight of static reservoir pressures, which are important for confirming fluid contacts and fluid density gradients. Methods of formation pressure testing have evolved over many years. Through this paper's case study, recent LWD and wireline pressure-testing technology are elaborated in depth, in relation to two sequential wells drilled offshore in the Kutai Basin. LWD pressure-testing operations were conducted in well XX-5 in a dedicated run after completion of drilling the section. The wireline test was conducted in well XX-4 as an open-hole logging run, along with the acquisition of fluid analysis data. Both systems were successfully utilized in the 6-inch hole sections of the subject wells, in a depleted reservoir, with the pressure overbalance expected to reach around 3100 psi in the pre-job planning stage. The average mobility was low in both sets of pressure test results, as also align with the reservoir's current depletion state. Challenges related to tight tests and lost seals in this mature field were experienced with both systems. The drilling environment and the formation's exposure conditions may have presented varying challenges; nevertheless, the same relatable quality has been achieved with both types of testing (LWD and wireline). This paper describes in detail the planning, design, and performance of pressure testing using LWD and wireline in the Kutai Basin. Comparisons between results are displayed to highlight the current character of the subject offshore field. This study aims to enhance future drilling and logging operations, by reviewing solutions from formation pressure testing technologies and to add value to mature and depleted field planning. Technical Categories: Geotechnical, Geoscience & Geophysics; Drilling Technology
An offshore gas-producing well recently encountered an increase in water production. The well featured multiple completion zones, creating ambiguity and uncertainty in the water source and production zone. Due to the significant deviation of the well, coiled tubing (CT) provided the means of conveyance for an advanced array of well diagnostic tools selected to evaluate the multiple downhole scenarios that may lead to the increase in water production, including completion failures, saturation depletion, and flow from unexpected sources. This paper discusses the integrated analysis and methodology behind the successful determination of the water source in an offshore gas-producing well. The deployed tools include a multi-detector pulsed-neutron tool (MDPNT), an advanced acoustic array leak detection tool (ALDT), and a suite of production logging tools. The logging suite was tailored to address the wealth of possible scenarios for the increase in water production. Logging was performed in shut-in and flowing environments to understand the behavior of the well in dynamic conditions. Following the acquisition, the data sets were integrated and analyzed, leading to the successful determination of the problem zone. The well featured two perforated reservoirs, each separated by packers and sliding sleeves. The deeper zone was determined to be water-saturated and should have been isolated by a closed sliding sleeve beneath a packer. MDPNT oxygen activation eliminated the possibility of channeling between the water-producing zone and the gas-producing zone. The packers in the well proved to be intact based on the interpretation of the ALDT acoustic noise data and the count rate reading of the MDPNT. The investigation then focused on the completion string jewelry and involved computing a two-dimensional (2D) radial flow map from beamforming of the ALDT-recorded acoustic noise activity around the wellbore, which revealed a closed sliding sleeve within the water-producing zone was likely leaking and, therefore, ineffective. The saturation results using the MDPNT in sigma mode indicated that the perforated reservoirs contained a low remaining gas saturation. Following the diagnosis, the operator ensured the sliding sleeve was closed reducing water production by more than 50%, resulting in an improved well performance. Compatibility with CT enabled the advanced suite of pulsed neutron, acoustic noise array, and PL wireline sensors to be deployed in a well with significant deviation. As the water production source was unknown, many possible scenarios had to be tested. Careful job planning and interpretation of the acquired log data eliminated scenarios and led to the conclusion that the completion integrity was compromised at a sliding sleeve, therefore enabling flow from a water-saturated zone.
Often, casedhole petrophysics provide essential information for reservoir surveillance and monitoring in mature field reservoirs for recovery optimization. One of the vital casedhole data acquisitions involves a pulsed-neutron tool for formation evaluation. The service company's recently developed multidetector pulsed-neutron tool (MDPNT) with a long-spacing detector provides a unique measurement [sigma, carbon-oxygen, and saturation gate (SATG)], which significantly helps improve sensitivity for formation gas saturation. The multidetector pulsed-neutron tool (MDPNT) is the only casedhole formation evaluation tool within the industry to be used with a memory system simultaneously acquiring the inelastic carbon/oxygen (C/O) ratio and capture (sigma) logging modes. The high-power battery pack provides up to 11 hr of continuous logging with superior data quality. A memory-based logging system provides advantages in terms of a smaller footprint, improved operational safety, and easier logistics handling, which results in significant operation cost reductions. A successful application of the first MDPNT memory logging on slickline deployment in Field A of Peninsular Malaysia is discussed. Pulsed-neutron data were acquired in the well with the objectives of validating hydrocarbon fluid types for additional perforation operations and determining current hydrocarbon saturation to derisk openhole log interpretation uncertainties and fluid contact delineations. The targeted sand is located above the top packer section, and based on openhole logs alone, there is a high uncertainty of distinguishing between the presence of oil and water. The well consists of a complex completion string with 3.5-in. tubing inside a 7-in. casing along with a packer and sliding side door (SSD). Gas trapped under the packer is a common scenario and poses another challenge in saturation computation. Post-data acquisition results exhibited a positive indication of oil presence within the targeted reservoir. Gas-oil contact (GOC) was successfully determined within one of the reservoirs despite the thin oil rim presence, which could be easily overlooked. The discovery has led to the assessment of a nearby well to be the potential add-perf candidate within the same reservoir for quick gain monetization. The add-perf operation was conducted in two reservoirs and flowed successfully at 500 B/D instantaneous production. The effort was well paid in reactivating an almost four-year idle well status with sustained production and a 0.2 MMSTB reserves addition. In other words, the three-phase pulsed-neutron analysis consisting of the C/O, sigma, and SATG combination has convincingly generated a robust saturation computation covering all the zones of interest. The case study described in this paper emphasizes the benefits of the MDPNT memory logging, particularly within a challenging offshore environment with a limited footprint profile and logistics arrangement, and yet successfully unlocked the low-hanging fruits for production enhancement.
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