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Abu Dhabi's onshore oil fields are generally mature and contain carbonate reservoirs with light oil and gas. Various well types have been employed, such as vertical, highly deviated, and horizontal wells with cased hole or openhole completions. Surveillance of wellbore and formation fluid attributes is essential for reservoir management decisions and hydrocarbon production enhancement. This paper discusses surveillance techniques to understand multi-phase flow characteristics and reservoir saturation. Formation saturation monitoring and production profiling have been performed actively using pulsed neutron logging (PNL) and array production logging (APL) techniques. Challenges in employing the APL method in Abu Dhabi onshore fields include (1) many wells are horizontal with barefoot completions, (2) horizontal sections extend typically more than 2000-ft long with irregular and undulating trajectories, and (3) wells contain asphaltene, debris, and other materials preventing optimal spinner flowmeter functionality. After reviewing each well condition, well environment-specific combinations of APL, nuclear production logging applications for holdups and water velocity calculations, and an advanced three-phase formation saturation analysis technique were determined. This approach overcame several challenges to deliver surveillance objectives. We demonstrate four case examples, delineating well-based production and formation saturation profiles in various conditions. Two nuclear measurements exhibiting different sensitivities to oil and gas were combined to compute three-phase formation saturation. When a horizontal openhole wellbore was severely under-gauged, the pulsed neutron-based holdup application was used to avoid an APL tool deployment that might result in tool damage and unsatisfactory data acquisition. Additionally, for wells with good wellbore conditions, pulsed neutron-based and APL-based holdup data sets were acquired, and analysis results were compared. A stationary water velocity calculation method when water cut was high was also adopted to identify downhole water sources, and in-situ water production profiles from APL and nuclear applications were compared. An effort to evaluate production profile and in-situ saturation effectively from highly deviated- and horizontal wellbores to improve hydrocarbon production is described. The delineation of production profiles and formation fluid distribution allowed operators to determine reservoir and production management strategies.
Abu Dhabi's onshore oil fields are generally mature and contain carbonate reservoirs with light oil and gas. Various well types have been employed, such as vertical, highly deviated, and horizontal wells with cased hole or openhole completions. Surveillance of wellbore and formation fluid attributes is essential for reservoir management decisions and hydrocarbon production enhancement. This paper discusses surveillance techniques to understand multi-phase flow characteristics and reservoir saturation. Formation saturation monitoring and production profiling have been performed actively using pulsed neutron logging (PNL) and array production logging (APL) techniques. Challenges in employing the APL method in Abu Dhabi onshore fields include (1) many wells are horizontal with barefoot completions, (2) horizontal sections extend typically more than 2000-ft long with irregular and undulating trajectories, and (3) wells contain asphaltene, debris, and other materials preventing optimal spinner flowmeter functionality. After reviewing each well condition, well environment-specific combinations of APL, nuclear production logging applications for holdups and water velocity calculations, and an advanced three-phase formation saturation analysis technique were determined. This approach overcame several challenges to deliver surveillance objectives. We demonstrate four case examples, delineating well-based production and formation saturation profiles in various conditions. Two nuclear measurements exhibiting different sensitivities to oil and gas were combined to compute three-phase formation saturation. When a horizontal openhole wellbore was severely under-gauged, the pulsed neutron-based holdup application was used to avoid an APL tool deployment that might result in tool damage and unsatisfactory data acquisition. Additionally, for wells with good wellbore conditions, pulsed neutron-based and APL-based holdup data sets were acquired, and analysis results were compared. A stationary water velocity calculation method when water cut was high was also adopted to identify downhole water sources, and in-situ water production profiles from APL and nuclear applications were compared. An effort to evaluate production profile and in-situ saturation effectively from highly deviated- and horizontal wellbores to improve hydrocarbon production is described. The delineation of production profiles and formation fluid distribution allowed operators to determine reservoir and production management strategies.
Water-in-oil emulsion represents a substantial volume of the produced water while the process of demulsification at surface remains costly. Accurately determining the source of water in oil producers with emulsion flow remains a challenge for production logging (PL). This paper presents a case study that shows how an innovative PL suite meets the main objectives of delivering a robust and accurate diagnostic of water ingresses and of informing an operational decision of a water shut off in an open hole gravel completion. After a history of deploying legacy centralized PL strings with sub-optimal probe and measurement capabilities in emulsion flow regimes, an operating company elected to deploy a third generation Production Logging Tool (PLT) which ultracompact length of 1m results from use of microelectromechanical systems (MEMS). The PL platform combines centralized measurements of pressure, temperature, Doppler, MML (CCL) with oriented azimuthal array holdups and flow speed sensors. The holdup measurements consisted of proven triphasic optical probes and conductivity probes and of newly developed micro-capacitances designed to sense micrometer water droplets in oil continuous phase. The PL survey was acquired on memory and deployed on slickline during well shut-in and at three different flowing rates. Very consistent and reliable gas holdup was measured by the triphasic optical probes through the whole acquisition. The water holdup was calculated using the micro-capacitance data as it proved to be the most accurate, in particular during the highest rate. The optical water holdup agreed well with the capacitance at intermediate and lower rates. The electrical probes were affected by water emulsion flow and stopped detecting water at flow speeds larger than 200 fpm (feet per minute). Excellent flow speed measurements were obtained with the robust micro-spinners covering a wide range of flow speeds from a few fpm up to 500 fpm. The main source of water was located at the bottom of the gravel pack completion. The PLT was run with an innovative combination of flow speeds and holdups sensors that allowed to reliably diagnose the water ingresses. Based on these results, a water shutoff intervention job was decided, implemented and coupled with a gas lift valve change to improve the gas lift injection that eventually led to a significant increase in oil production close to 1000 bbl/day and 10-point reduction in water cut. The extremely compact PLT with collocated holdup and flow speed sensors enable to deploy array production logging with limited rig up height. State of the art methods for measuring water holdups such as resistivity or conductivity fail in these extreme conditions due to the extremely small size of water droplets. The newly developed micro-capacitances are designed to sense micrometer water droplets in oil continuous phase, which is typically of emulsion flow.
A field is a faulted anticline structure lying in a deepwater turbidite environmental setting, which consists of four main sand bodies that were targeted over two phases of development. The field is accessed via a Tension Leg Platform (TLP) structure, about 100KM from the shores of Sabah, with water depths of around 1600ft. Most of the historical production in the field comes from two reservoirs, which have had varying degrees of performance across the field with challenges ranging from secondary gas caps, to increasing water cuts and formation impairment. Part of the field management strategy has been to either introduce water injection to maintain pressure, or GOR limit relaxations when additional pressure support is not possible. Difficulties that add to the field is the non-uniform depletion of the reservoir due to either structural compartmentalization (which is highly prevalent in this field) or sedimentary complexities due to thin bed production, uncertain fluid movements and skin introduced via fines migration. Since 2018, multiple logging campaigns have been conducted on both reservoirs to characterize and diagnose the nature of inflows with various solutions proposed depending on the outcomes. To date, the field has employed multiple gas shut-offs, water shut-offs and acid stimulation jobs that have led to highly profitable successes along with failures that have informed future and ongoing work in the field. This paper will attempt to summarize the various interventions made on the field and the subsequent solutions proposed and implemented, which has led to significant incremental gains from the brownfield where successful and lessons learnt where solutions proposed were less optimal. The multiple campaigns conducted on this field has also led to great efficiencies in the interfaces between the various groups, from vendors, to wells, asset and subsurface with results and mitigations regularly proposed and supported by the various joint venture partners and regulators in the field. The uniqueness of the challenges faced in this Deepwater field is the ability to intervene ‘relatively’ cheaply to diagnose the problems given the dry-tree nature of the TLP, as opposed to subsea type wells requiring huge operational costs that are commonly found in other similar Deepwater type developments. This provides the unique opportunity to trial multiple state of the art type intervention techniques where even the smallest possibility of success potentially pays off for multiple campaigns. The technical learnings should therefore be highly applicable to many assets, and the ways of working and interfacing that will be demonstrated should be replicable in other places.
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