Inflow-Control Device, Inflow-Control Valves Aid Kuwait’s First Smart Multilateral Well
The smart multilateral well has assisted in addressing premature water breakthrough, has enhanced water-free oil production, and has facilitated uniform depletion, which results in improved hydrocarbon recovery.
Kuwait’s first smart Level-4 multilateral well was completed in the Burgan reservoir by combining a Level-4 junction with stacked dual-lateral completion with a customized viscosity-independent inflow-control device (ICD), two customized inflow-control valves (ICVs), downhole gauges, a wide-operating-range electrical submersible pump (ESP), suitable wellheads, a tree, and integrated surface panels for real-time data monitoring. The smart multilateral well has assisted in addressing premature water breakthrough, has enhanced water-free oil production, and has facilitated uniform depletion, which results in improved hydrocarbon recovery.
The Minagish field in west Kuwait (Fig. 1) is a north/south-trending anticline with hydrocarbon contained in six major reservoirs (sandstone and carbonate) ranging in age from Early Jurassic to Late Cretaceous. The Burgan sandstone reservoir lies at the crest of the Minagish field.
The lower section of the Burgan sandstone reservoir consists of a braided river system with stacked-channel sand bodies that have very high horizontal and vertical permeability (on the order of a few darcies) and are associated with an underlying active aquifer. The combination of high oil viscosity, oil-wet reservoir characteristics, and very high water mobility associated with very high permeability and the presence of fault networks connected to the aquifer accelerates water movement inside the reservoir and results in premature water breakthrough in existing vertical and horizontal wells, despite maintaining highest standoff from the oil/water contact.
Smart-Multilateral-Well Architecture and Design
The smart-multilateral-well design was customized for ICD completion at the sandface for both the main-bore and upper-lateral intelligent completion including two ICVs, downhole gauges, feed-through packers, and a Level-4 cemented junction to provide fullbore access to the main bore and upper lateral. A schematic of the smart multilateral well is shown in Fig. 2.
ICD Selection and Design
The following objectives were considered for completion of the horizontal openhole section of the main bore and upper lateral of the smart multilateral wells:
- Facilitate uniform inflow across the entire horizontal production section of both the main bore and upper lateral.
- Control water production from relatively high-permeability layers upon water breakthrough.
- Allow automatic adjustment to compensate for changes in well-inflow profile over the production life of wells.
- Provide uniform sweep efficiency across sandface.
- Minimize annular flow.
- Minimize pressure drop through ICD housing to improve flowing bottomhole pressure (FBHP) in main bore and upper lateral.
- Minimize bypassed-oil regions, and maximize oil recovery.
- Maximize production life of wells.
On the basis of these objectives and by considering the physics and chemistry of fluid flow inside the Burgan reservoir under operating conditions of a smart multilateral well, the most suitable nozzle-type ICD completion was selected.
Appropriate ICD-completion design is the main factor for successful ICD-completion performance over the production life of wells. The ICD-completion design for smart multilateral wells of the Burgan reservoir was created by considering the objectives of ICD completion as well as the flow characteristics of nozzles. To achieve the appropriate design for ICD completion, reservoir characterization was performed by acquiring permeability from Stoneley waves and from log porosity/permeability correlation calibrated with core data. The appropriate reservoir segmentation to achieve effective zonal isolation with isolation packers was identified as a critical factor in minimizing annular flow, addressing premature water breakthrough, and minimizing water production. Effective wellbore segmentation along the well trajectory was achieved by plotting the permeability profile; porosity profile; water-saturation profile; reservoir-pressure profile; reservoir-fluid properties; and geological settings of the reservoir, including faults and fractures interpreted from high-resolution 3D-seismic and image logs recorded during drilling and geosteering.
Intelligent-Completion Selection and Design
Intelligent completion of the smart multilateral wells comprises two ICVs and downhole gauges to control production selectively from main bore and upper lateral in order to achieve optimum production management to minimize water production, maximize sweep efficiency, and maximize oil recovery. A schematic of the intelligent-completion system for both the main bore and upper lateral is shown in Fig. 3. The N+1 hydraulic-control-line system was selected for smart multilateral wells: The two hydraulic ICVs and one hydraulic ball valve require four hydraulic control lines, three for opening the valves and one for a common close control line. One electrical control line is installed for downhole pressure and temperature gauges.
The appropriate ICV design plays an important role in achieving desired objectives from a smart multilateral well. The 10-position hydraulic ICVs selected for both main bore and upper lateral were designed on the basis of production- and reservoir-management needs and to eliminate crossflow between the legs. The ICV design was customized by considering the inflow performance with the ICD completions of the main bore and upper lateral, fluid properties, and ESP completion constraints to meet the well-production target. A multiposition ICV consists of inflow ports positioned linearly. Opening and closing the ports is controlled by a sliding sleeve actuated from surface through a hydraulic control line. The flow area at any position of the valve is the cumulative flow area of all the positions below it including the flow area of that particular position.
The fully open 10th position of the ICV is designed to provide a minimal pressure drop to impose no restriction to the flow. The other valve positions were designed to provide choking capabilities evenly to manage production from each lateral.
The customized design of the flow-control trim of an ICV is the main factor for ensuring ICV performance at specific well-production conditions. Each ICV position has a unique port size and geometry that satisfy the required pressure difference between the inflow and the outflow curves for the most likely cases of main bore and upper lateral.
Life-Cycle Production Monitoring and Reservoir Monitoring
The smart multilateral wells facilitate adequate reservoir monitoring and production monitoring by acquiring real-time data from downhole sensors without well intervention.
Reservoir-Pressure and -Temperature Measurement. As shown in Fig. 3, the lower annulus and tubing gauge measures pressure and temperature in the annulus between the production casing and lower ICV. The annulus pressure can be converted to the heel pressure of the main bore ICD completion by proper correction for frictional pressure loss and hydrostatic pressure. By closing the lower ICV as per a required shut-in period, the annulus gauge, after correction for hydrostatic pressure, will provide the reservoir pressure of the main bore. The actual FBHP and reservoir pressure along with the temperature of the main bore are obtained as required for reservoir monitoring and management. In addition, pressure-buildup analysis also can be conducted to evaluate the well-testing parameters for reservoir monitoring and performance evaluation. Similarly, the reservoir pressure, FBHP, and well-test parameters for the upper lateral can be calculated through the upper annulus and tubing gauge.
Water-Cut Measurement of Main Bore and Upper Lateral. As shown in Fig. 3, the lower annulus and tubing gauge and the lower tubing gauge are separated by more than 100 ft true vertical depth (TVD), which allows for the measurement of pressure in the tubing at two different points. By knowing the pressure difference and with proper correction for friction, the difference in hydrostatic pressure can be obtained and the water cut of the main bore can be calculated. See the full paper for the equations.
Similarly, for the upper lateral, the upper annulus and tubing gauge and the upper tubing gauge are separated by more than 100 ft TVD, which allows for measurement of pressure in the tubing at two different points. By knowing the pressure difference and with proper correction for friction, the difference in hydrostatic pressure can be obtained and the combined total water cut of the main bore and the upper lateral can be calculated. By subtracting the water cut of the main bore from the total water cut, the water cut of the upper lateral can be calculated.
Flow Rate for Main Bore and Upper Lateral. Main Bore. As shown in Fig. 3, the lower annulus and tubing gauge measures the differential pressure through the lower ICV at a particular ICV position. See the complete paper for the equation to obtain the total liquid rate in B/D through the ICV.
Upper Lateral. As shown in Fig. 3, the upper annulus and tubing gauge measures the differential pressure through the upper ICV at a particular ICV position. See the complete paper for the equation to obtain the total liquid rate in B/D through the ICV. The oil and water rate can be calculated by knowing the water-cut value of the upper lateral.
Best Practices Adopted
Kuwait’s first smart multilateral well was drilled and completed by using the following best practices.
Optimum Well Location and Wellbore-Trajectory Optimization. A multidisciplinary team was formed by involving geologists, petrophysicists, petroleum engineers, reservoir engineers, drilling engineers, and experts from service companies to select well locations and to optimize the well trajectory to meet Level-4 multilateral-junction requirements, ICD-completion requirements, and intelligent-completion requirements.
Operational Planning and Execution. The drilling and completion of smart multilateral wells involved various international contractors to supply well hardware and services. To manage the project during the planning and execution phases, well-established project management and interface management were developed. The well-drilling and -completion program was prepared by involving varying multidisciplinary expertise. In addition, frequent operational meetings were held to monitor project execution and take necessary, timely action.
Drilling and Geosteering. During drilling, the well trajectory was optimized using real-time geosteering to place the well in the sweet spot, avoiding high-water-saturation areas and minimizing exposure to faults and potential conduits for premature water breakthrough. The geosteering was accomplished by using advanced and innovative technologies, including azimuthal deep-resistivity measurements, at-bit measurements, and density images to correct well positioning and locate fault areas. High-resolution geochemical analysis was used in real-time to identify geochemical proxies and allow geochemical steering. Also, a new version of the sonic log was used to calculate permeability through Stoneley-wave energy dissipation, which was used for ICD completion design.
Adequate Wellbore Cleanup. Effective wellbore cleanup and wellbore-debris management were identified as key factors for successful Level-4 smart-multilateral-well completion and were achieved by proper wellbore cleanup during various operational phases using the advanced wellbore-cleanup tools, including high-capacity magnetic tools, debris catchers, casing scrapers, and brushes.
The smart multilateral wells achieved remarkable success in terms of sustained oil production by addressing severe water breakthrough and provided uniform reservoir depletion. Further, they facilitated improved reservoir management. The well-performance results are shown in Fig. 4.
This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 159261, “Novel Design and Implementation of Kuwait’s First Smart Multilateral Well With Inflow-Control Device and Inflow-Control Valve for Life-Cycle Reservoir Management in High-Mobility Reservoir, West Kuwait,” by Om Prakash Das, Khalaf Al-Enezi, Muhammad Aslam, Taher El-Gezeeri, and Khalid Ziyab, SPE, Kuwait Oil Company; and Steven R. Fipke and Steven Ewens, Halliburton, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 8–10 October. The paper has not been peer reviewed.