This paper presents a workflow method that has been designed to improve well placement accuracy, enhance decisionmaking and decrease cycle time through rapid geologic model updates. This workflow was applied successfully to a horizontal well located in a giant oil and gas field offshore Abu Dhabi, United Arab Emirates. This workflow involves geomodeling, well design, synthetic log creation, real-time geosteering, and updating the geological model while drilling. Drilling a horizontal well in this environment presents several challenges due to complex geology, heterogenous carbonate reservoir and layer thickness. In addition, there are many uncertainties reflected in the 3D geological model and while drilling. The primary aim of this workflow is to minimize drilling time with maximum efficiency and optimum well placement. This is achieved through designing the well in the same model centric environment where the geological model was built allowing access to all available data and information for accurate well placement. Secondly, to reduce non-visible loss time and take faster decisions using real-time information. Thirdly, to evaluate associated geological uncertainties in 3D models. Finally, the use of the latest technology available in the market to meet field development requirements. Great value was added when a 3D model was generated and updated in real time, in addition to the forward-modeling technique that assists the operation geologist to geosteer within the thin layer of the heterogeneous carbonate reservoir in order to achieve the optimum well placement in the minimum amount of time.
Including "smartness" in your field does not necessarily add additional expenditures. ADNOC Offshore piloted a new well completion design combining Interval Control Valves (ICVs) in the shallow reservoir and Inflow Control Devices (ICDs) in the deeper reservoir, both deployed in a water injector well for the first time in the company. The objectives were to improve reservoir management, reduce well construction complexity and achieve one of the main business targets of cost optimization. This paper covers the subsurface study, detailed well construction design, completion deployment, well intervention and overall well performance in commingled injection mode. A multi-disciplinary study was conducted based on updated reservoir data available after the first two years of production in a heterogeneous multi reservoir field. This study showed the possibility of replacing the upper horizontal drain by a deviated perforated section. The authors identified the need of completion compartmentalization to overcome challenges such as high reservoir heterogeneity and uneven pressure depletion enforced by non selective acid stimulation. As part of the evaluation, a simulation was performed to evaluate the expected injection performance across the four zones with different combinations of ICVs and ICDs in order to cater for different injection scenarios. As a result of the integrated analysis, a new well completion design was deployed to optimize a Dual Horizontal Water Injector into a Single Smart Completion with 3 Inflow Control Valves (ICVs) covering the upper perforated zones and 14 Inflow Control Devices (ICDs) with sliding sleeves across lower lateral reservoir. Cost savings and reduction of rig time was achieved with this new completion design demonstrating very pro-active participation from all involved teams, ADNOC Offshore and Service Companies. The requirements to complete high and low permeability zones in one single well can be successfully accomplished. Firstly, mitigation of early water breakthrough is achieved by incorporating surface water injection control in high permeable zones and secondly, the injection target for the low permeable reservoir is also delivered. Building on the successful results and captured lesson learnt, this new well completion design provided the capabilities to optimize the water injection plan while reducing costs. Therefore, the project has passed the trial phase and the team proposed its implementation.
Sourceless well logging (logging without using traditional chemical sources) has become more attractive in certain locations because of evolving government regulatory and HSE requirements. LWD sonic tools provide opportunities to operators for both well placement and formation evaluation. For the first time in the UAE, an LWD acoustic tool was added to a bottomhole assembly (BHA) to acquire sourceless porosity measurements to help stay in the porous sub-layers in the target reservoir. In comparison to more traditional nuclear measurements, LWD sonic has a superior depth of investigation that is less affected by standoff and a driller-friendly BHA free from stabilizers. Based on the evaluation of offset data, which indicated excellent correlation of sonic vs. density/neutron measurements, we decided to provide shear porosity in real time owing to the sequence stratigraphy and corresponding energy partition. A post-job comparison with density/neutron data acquired in a wipe run was also conducted to verify the sensitivity of real-time acoustic porosity measurements for both well-placement and formation-evaluation purposes. Sonic-derived porosities were found to be instrumental in the real-time decision making needed to keep the well the in higher porous sub-layers. Current developments, including real-time azimuthal sonic together with considerations of integrating acoustic and NMR measurements in both petrophysical modeling and field applications, show promise in providing reliable sourceless porosity estimation in these formations. This case history delivered a BHA free from radioactive chemical sources. Safe drilling objectives as well as maximized productivity per unit lateral length were achieved despite the potential risks associated with the faults that were observed in the pilot hole. Introduction With a global focus on exploring oil and gas with minimum environmental impact, the regulations in the region are very strict on adhering to zero harm to the environment. One of the most stringent laws in place is with regards to the abandonment of radioactive sources in the well in the event of a stuck pipe. ADMA OPCO is an active player in helping service companies develop and improve on their “sourceless” alternative technologies to reduce potential risks associated with stuck pipe. Real-time acoustic measurements were used for well-placement purposes in Field A, which is one of the giant fields located in offshore Abu Dhabi. Oil was discovered in 1958, and production began in 1962. Down-flank water injection started in 1973 followed by crestal gas injection in 1994. The Arab reservoir in Field A was formed from regressive cycles of sedimentation divided into four highly heterogeneous sub-reservoirs (labelled in ascending order from A to D (Fig. 1)). The principal oil-producing reservoirs are Arab zone C and Arab zone D, whereas Arab zones A and B still remain undeveloped. Based on the core description, the Arab reservoir section is mainly composed of three lithologies, namely, anhydrite (purple shading), dolomite (green), and limestone (light blue), as shown below in Fig. 1.
Heterogeneous carbonates formations have unique challenge to obtain representative permeability values. During the exploration phase and due to the limited number of wells and technologies, the initial formation evaluation might be misleading. The permeability results from conventional core analysis (CCA) might be significantly under evaluated because vertical interference tests from a wireline formation tester and production tests show different results. This paper describes a case study in offshore Abu Dhabi and solutions that should be assessed to overcome this challenge. An integrated approach was performed to determine the possible causes of permeability mismatch between cores, logs, wireline formation testers and production tests in this field. Based on logs and core data, the reservoir was subdivided into different layers and further refined using permeability indices from NMR logs. Formation testers with advance measurements were used to evaluate effective vertical and horizontal permeability of a single layer. The production testing covering several layers was used to fine-tune subzone permeability and subsequent flow units. The results from this study show that permeability given by CCA was somewhat misleading due to physical limitations from core plugging. The detailed core description and well-test data indicate that a significant portion of flow passes through high-permeability (vuggy) sections of the formation that cannot be measured by plugs. A formation tester was applied to check vertical and horizontal permeability in one productive zone. Various methods were integrated in the study to reconcile the unexpected high productivity of the sub-layer and explain permeability distribution from different tools. This case study provides a useful example in identifying and explaining data from reservoirs where the dynamic well productivity data differs from static data prediction.
The ultimate success of an offshore field startup depends on the strategy and integration within an organization. Even more challenging is managing the dynamic interface of subsurface and surface project delivery through the design, construction, hookup, commissioning, and startup operations. This paper presents the case study of a new field startup in Abu Dhabi from the early concept selection through the critical startup phases. Integrated multi-discipline approach underpinned the successful startup when the field achieved first oil production ahead of schedule on February 2015 and exceeded expectation despite the backdrop of global sharp decline in oil price. This paper highlights the technical and functional preparation put in place by the subsurface and surface teams to ensure full integrated readiness and plan-in-place for production start-up. It also outlines the challenges encountered to achieve operational performance and the major lessons learned from the journey. The results demonstrated in this paper shows that an integrated and cooperative approach is key in dealing with delays, prioritization, execution of processes, projects and operations. The lessons learned from subsurface and surface technical preparation, through surface project engineering and delivery phases are presented. Successful management was critical in handling the drilling rigs and barge logistics, offshore installation and commissioning phases, and simultaneous operations during the production start-up and ramp-up of the field. In addition, while encountering pressures to minimize rig time and execute the extensive data gathering program, good team synergy ensured that the milestones were successfully met even with the additional limitation of skilled technical resources. Finally, illustrated in this paper are best practices applicable for new offshore field startups. This proves that even with the financial-demanding outlook and market-down conditions, the successful startup of a new field is essential and visible.
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