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OPECS
Case Study: First Multistage Fracturing SIMOPs with Concurrent Drilling Operations in Clair Ridge Field, North Sea
Bird, Anastasia (OPECS) | Lumsden, Jim (OPECS) | Paterson, James (OPECS) | Marshall, Erin (OPECS) | Sibbett, Steve (OPECS) | Hoad, James (OPECS) | Stanley, bp. Reginald (OPECS) | Norris, SLB. Mark (OPECS)
Abstract Hydraulic fracturing has demonstrated its value in terms of production uplift for the Clair Field from the first hydraulically fractured well on the Clair Phase 1 Platform. The Clair Ridge Platform, the second phase of the Clair Field development, has been on production since 2018. The Ridge area of the Clair Field is a naturally fractured part of the reservoir. The natural fractures provide productivity drive to the Ridge producers. However a few wells that did not encounter sufficient natural fractures, have delivered production results below expectations. Consequently, this caused increased interest in hydraulic fracturing to protect the base and provide additional production uplift. Hydraulic fracturing in naturally fractured reservoirs poses certain challenges and uncertainties for the design and execution. The candidate well was selected based on absence of natural fractures, poor matrix quality and low initial production rates. The well has been pre-produced, which further complicated the stimulation scope. Enhanced fracturing modeling with the use of 3D cube from full field model aided stimulation design by integrating hydraulic fracture placement with mapped faults and reservoir unit boundaries. Fracturing offshore as a wellwork campaign is an intensive and complex scope. The inefficiencies in fracturing after the upper completion on platforms not specifically designed to support hydraulic fracturing operations cause delays to operations and realizing the production benefits. A key challenge for the Clair Ridge Platform was to build on the standalone fracturing operation on the Clair Phase 1 Platform and deliver a similar intervention-based stimulation, but while a fast-paced drilling program was ongoing, which posed a big challenge for simultaneous operations (SIMOPS). This paper documents how the first multistage fracturing on the Clair Ridge Platform was performed in parallel with active drilling and production, significantly increasing the intervention complexity. Operationally, the fracturing set up involved wireline for gas lift valve replacement, coil tubing (CT) for sleeve manipulation and clean out between stages, a stimulation vessel for pumping and a well clean up package to separate solids during clean out and initial flowback. The well productivity index post-stimulation has increased five-fold during transient period and three-fold stabilized. Chemical tracers were used to enhance the understanding of zonal contribution to production. Proving the feasibility of ‘offline’ offshore stimulation during active drilling, the project has in turn revealed many challenges. These challenges are documented along with detailed lessons learned on optimizing SIMOPS for future operations. New insights include considerations on design and hydraulic fracture placement in naturally fractured reservoirs, with lessons learned for managing pressure dependent leak-off. It opens an opportunity to hydraulically fracture zones of higher fracture density to further enhance production for the wells on the Clair Ridge Platform.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology (0.66)
- Europe > United Kingdom > Atlantic Margin > West of Shetland > Faroe-Shetland Basin > Rona Ridge > Block 206/9 > Clair Field (0.99)
- Europe > United Kingdom > Atlantic Margin > West of Shetland > Faroe-Shetland Basin > Rona Ridge > Block 206/8 > Clair Field (0.99)
- Europe > United Kingdom > Atlantic Margin > West of Shetland > Faroe-Shetland Basin > Rona Ridge > Block 206/7 > Clair Field (0.99)
- (3 more...)
An Efficient Chemical Treatment to Tackle Low Productivity of Challenging Tight Dolomite: Wormholing and Remediation of Scale-Based Damage
Nazari Moghaddam, Rasoul (Nouryon) | Van Doorn, Marcel (Nouryon) | Dos Santos, Auribel (Nouryon) | Lopez, Fabian (Nouryon) | Ulloa, Mario (OPECS) | Bocaneala, Bogdan (OPECS) | Pitts, Michael (OPECS)
Abstract Economical production from unconventional reservoirs including tight dolomite require some forms of stimulation techniques to increase the effective contact areas between wellbore and formation. However, productivity improvement of these formations with conventional techniques (e.g. acid stimulation) is very limited and mostly unfeasible. In this paper, an efficient chemical treatment is proposed to stimulate tight dolomite formation through wormholing mechanism and scale-based damage removal. The formation damage in tight reservoirs are much more severe due to the smaller pore/throat size. Among them, the scale-based permeability impairment or phase trapping can cause significant production lost. In this study, the proposed treatment fluid is used to remove the scale-based formation damage, mostly caused by drilling mud. To this aim, the damage removal efficiencies of dolomite cores, artificially damaged by scale precipitation, were investigated after HPHT coreflood treatment. In addition, the performance of the treatment fluid was evaluated as a mean to bypass the damaged zones around hydraulic fractures (caused by liquid phase trapping or significant net stress). To evaluate this, a series of coreflooding experiments were also performed on untreated tight dolomite cores and the feasibility of the wormholing mechanism was studied. The permeabilities of tight dolomite rocks were measured before and after the treatment. To visualize the wormhole propagation inside the cores, computed CT scanning were performed. The rock-fluid interaction was also investigated by analyzing the effluent samples by ICP. The main mechanism of this treatment technique is pore body/pore throat enlargement by slow rock dissolution. From the pore scale analysis, it is found that even at lower concentrations, the active ingredient reacts with rock minerals. A damaged dolomite core was also treated, and the results showed that the removal of Barite-based scale can be achieved even in the presence of native calcite or dolomite minerals. Also, it is found that wormholing can be only achieved at certain concentrations (>10 w%). It also depends on the injection rate and other field conditions such as temperature. Even at low concentration, the rock permeability of the damaged dolomite core can be increased by a factor of 35 (Kf/Ki=35). Finally, dolomite reservoir cores (25-30 μD) were treated at low injection rates (0.08-0.1 ml/min) imposed from the well injectivity condition. It was shown that despite an order of magnitude lower injection rate (compared to those in conventional acidizing) still an optimum injection rate is needed to extend the wormhole across the core. It is also verified that the active ingredient can be used in alcohol-based solutions for special applications such as tight gas and gas condensate reservoirs. The corrosion rate is far below the accepted corrosion level of 0.05 lb/ft2 and it is fully compatible with other additives and high salinity brines. The proposed treatment method is cost effective and experimentally proven to be efficient and long-lasting. Such treatment is recommended to tackle the low productivity of unconventional tight reservoirs. This treatment can be even applied to remove the additional formation damages usually caused during conventional stimulations such as hydraulic fracturing to boost the production.
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Dolomite (1.00)
- Geology > Mineral (1.00)
Appraising the Development Potential of Ekofisk Over Tor Formation in the Halfdan Field, using a Multi-Disciplinary Approach to Well Planning and Applying Advances in Technology to Enhance Well Placement, Completion, Productivity and Recovery
Andreev, Anton (Total E&P) | Pitts, Michael (OPECS) | Hoover, Andrew (Total E&P) | Elhassan, Eyad Mohamed (Total E&P) | Bexkens, Felix Sebastian (Total E&P) | Datta, Sudipto (Total E&P) | Singh, Amit (Total E&P) | Lund, Espen (Total E&P) | Panos Gomez, Luis (Total E&P)
Abstract Demonstrating a viable development for the Ekofisk reservoir directly above the producing Tor reservoir in the Halfdan Field (Danish North Sea) has historically been challenging. A recent well shows the value of cross-disciplinary collaboration and new technology to maximize recovery and mitigate reservoir and drilling risks. Specifically, 4D seismic was utilized when planning the well, while placement was optimized by using advanced geosteering tools. Well optimization was further enhanced by adopting novel completion and stimulation technologies. Pressure data and 4D seismic show that Tor and Ekofisk are in dynamic communication, but the degree of communication varies locally. The integration of 4D seismic with other disciplines’ input succeeded in optimizing the well placement and narrowed the significant pore pressure uncertainty along the 12,000-ft reservoir section. To maximize well length within the target zone and reduce the risk of being faulted out of the target reservoir deep resistivity was used to steer the well in the optimal layers. This contributed to 99% of the reservoir section being placed in the target zone. Lessons learnt from an earlier appraisal well and modest production experience in this part of the Ekofisk reservoir helped to justify the choice of selective completion zones (Sliding Side Door) in the inner part of the horizontal drain in order to minimize the impact of potential water or premature water breakthrough from high-rate injection wells located in the underlying Tor reservoir. This decision was validated after drilling the inner part of the well, where water-swept zones were encountered in the heel, followed by a long gas pay zone in line with 4D seismic signal in the remainder of the inner well section. To mitigate the risk of an unwanted fracture connection and increase contact with the tight oil-saturated reservoir, a novel stimulation and completion technology was successfully deployed in the outer 6-inch open-hole section of the well. The acid needles completion, deployed across a 3,000-ft reservoir interval and comprising 224 needles deployed by pumping acid, was the first installation of its kind in the Danish North Sea. For the acid needles completion, this installation holds two distinctions: the largest number of acid needles installed in a well, and the combination of the acid needles completion with a different completion system in a single lateral for the first time.
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Time-Lapse Surveying > Time-Lapse Seismic Surveying (0.86)
- Europe > United Kingdom > North Sea > Central North Sea > Utsira High > PL 006 > Ekofisk Formation (0.99)
- Europe > Denmark > North Sea > Danish Sector > Central Graben > Block 5505/13 > Halfdan Field > Maastrichtian Formation (0.99)
- Europe > Denmark > North Sea > Danish Sector > Central Graben > Block 5505/13 > Halfdan Field > Danian Formation (0.99)
- (4 more...)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Conformance improvement (1.00)
Multilateral Multistage Hydraulic Fractured Offshore Wells; A New Trend in Completion Design and Optimization for More Effective Field Development
Bocaneala, Bogdan (OPECS) | Norris, Mark (OPECS) | Conrad, Joel (Packers Plus) | Tomlins, Andrew (OMV) | Bramald, James (Ithaca Energy) | Airnes, Jamie (Ithaca Energy)
Abstract Recently two multilateral horizontal wells have been completed offshore using dedicated multistage hydraulic fracturing completions. The first well, located in the Central North Sea (referred to as ML-CNS), was stimulated using acid fracturing; while the second well, located in the Black Sea (referred to as ML-BKS), was stimulated using proppant fracturing. This paper presents the different drivers, challenges and lessons learned for each well while emphasizing the well construction and stimulation methodologies developed for the different reservoirs and field characteristics. The field development drivers for drilling and completing these offshore hydraulic fractured multilateral wells, a first of their kind globally, was different for each case. The objective of the first project, initially considered uneconomic, was to engineer a technical solution for completion and production of two separate reservoirs with only one subsea well. The second project was seeking to optimize infill drilling from the last available slot on the offshore platform to maximize reservoir contact and production in the same reservoir. ML-CNS was a TAML Level 2 completion with a 14-stage, 5 ½" multistage completion run in each lateral and set-up for sequential acid fracturing. Operationally, the first lateral was drilled and stimulated, followed by the drilling and stimulation of the second lateral, using the drilling whipstock to navigate through the multilateral junction. ML-BKS was a TAML Level 3 completion that had a 6-stage, 4 ½" multistage completion installed in each lateral, which were proppant fractured following a sequence designed to minimize the jack-up rig time required. Both legs were drilled and completed prior to starting the stimulation, access to either lateral was achieved with the existing workover unit on the platform by manipulating a custom designed BHA. The lessons learned from the first project executed in the North Sea were able to be transferred and applied to the second project in the Black Sea to allow for a more efficient and confident completion solution. Led by varying economical and regional constraints, the key factor for both wells centered on delivering operationally simple and reliable multilateral completion designs to economically meet the field development strategy in place. To the knowledge of the authors and following subsequent literature research, both wells are a worldwide first for an offshore multilateral well completed with multistage acid fracturing and multistage proppant fracturing, and together they represent a new trend in cost-effective offshore field development through well stimulation. The successful case studies for both wells with the combined analysis of the benefits, challenges, and lessons learned will provide a guide and instill confidence with operators who find this approach beneficial with a view to applying it in other assets.
- North America > United States (1.00)
- Europe > North Sea (0.90)
- Europe > United Kingdom > North Sea > Central North Sea (0.47)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6a > Stella Field > Stella Ekofisk Formation (0.99)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6a > Stella Field > Stella Andrew Formation (0.99)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6a > Harrier Field > Tor Formation (0.99)
- (15 more...)
Abstract The paper aims to present the successful execution of the first offshore multilateral well completed for multistage high-pressure proppant stimulation - in the Black Sea, offshore Romania. The paper describes the drivers that lead the operator to trial a multilateral well as well as cover the considerations made in selecting, defining and executing the final completion solution with a review of the lessons learned. With only one platform slot left and a significant undrained area of reservoir the operator had to maximise the hydrocarbon recovery through a single well which, due to pressure to increase the operator's daily production, had to be finalised in just one year. Building on field experience gained since 2008 in drilling and completing for multistage proppant stimulation a detailed screening and evaluation of multilateral completion technologies was performed. The focus was on developing a concept that would minimise risks during execution while meeting cost and lead time objectives, which necessitated customising the chosen TAML Level 3 completion design and installation methodology. To maximise rig-time efficiency the well was executed in two phases: 1) drilling and lower completion installation of both branches with a drilling rig and 2) stimulation and upper completion installation with the platform's workover rig. With six stages in each lateral the high-pressure stimulation was executed by a converted supply vessel in four sailings, necessary to reload materials. To meet the delivery schedule, ensure simplicity and utilise operator experience the completion was realised with no dedicated multilateral hardware, rather, through the effective use of standard multistage stimulation open hole completion equipment and appropriately engineered bent joints to exit the main bore. With initial production rates higher than anticipated, the multilateral well completed in this manner has proven to be considerably more economic than drilling two horizontal wells with equivalent reservoir coverage. The success of this well serves as a proof of concept and provides increased confidence in delivering reliable, cost effective multilateral wells even under tight time constraints and in areas and/or operators with no history of multilateral well completions
- Europe (1.00)
- North America > United States > Texas (0.28)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Well Completion (1.00)
Abstract A North Sea case study detailing the completion and stimulation design of the world's first offshore acid fractured multistage dual lateral will be presented. The key driver behind this subsea completion technology and stimulation program was to implement a cost effective completion solution that reduced field development costs. The completion technology selected provided an economically viable and low-risk solution in an economically challenging hydrocarbon environment. The completion design was developed to access two separate carbonate gas reservoirs from a single main bore. The stimulation program for the two horizontal laterals was modeled using reservoir characteristics and key considerations. The stimulation program maximized resource efficiency by utilizing the fluid capacities available within one sailing of the stimulation vessel per lateral, totaling 28 acid fracture treatments. This novel offshore acid fractured dual lateral was drilled, completed and stimulated within three months. The horizontal section of the motherbore was completed using a 14 stage openhole multistage completion solution in three days. To reduce time on location, the well was stimulated after reaching setting depth via a tie-back fracture string. The motherbore was stimulated with individual and distributed acid fracture treatment via sequential ball-activated sliding sleeves. Once operations were complete for the motherbore, a whipstock packer was set and the second horizontal wellbore (Leg 2) drilled. The E1 Leg 2 wellbore was completed in only two days using the same technology and setup as the motherbore. Once the bottomhole completion was set, Leg 2 was stimulated with 14 stages of acid fracture treatments, using the same sized ball-activated sliding sleeves as in the motherbore. By implementing a flexible low cost completion solution and maximizing the resources available during stimulation, the world's first offshore acid fracture multistage dual lateral was successfully completed, requiring only one subsea wellhead and tree. The completion and stimulation program of this dual lateral project provided a high value solution to North Sea operations by minimizing time, resource utilization and expanding experience for future ventures.
- Europe > United Kingdom > North Sea (0.55)
- Europe > North Sea (0.55)
- Europe > Norway > North Sea (0.45)
- (2 more...)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6a > Harrier Field > Tor Formation (0.99)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6a > Harrier Field > Harrier Formation (0.99)
- Europe > United Kingdom > North Sea > Central North Sea > Central Graben > Greater Stella Area > Block 30/6a > Harrier Field > Ekofisk Formation (0.99)
- (3 more...)