Multilateral wells to achieve Maximum Reservoir Contact (MRC) have been widely implemented in a number of new carbonate fields' development in Saudi Arabia, resulting in substantial financial improvement of these assets. The successes achieved with this well architecture justified extending its use into a sandstone oil field that has been characterized with heterogeneous and poorly consolidated sandstone formation. This paper chronicles the multi-disciplinary approach and processes employed to evaluate, plan, and execute the first trilateral well in an unconsolidated heterogeneous sandstone reservoir in Saudi Arabia. The objectives of the ML well are to maximize reservoir contact to enhance sweep efficiency and improve well productivity and to promote the ML application in this complex field to extend field's production plateau. Initial well construction involved side-tracking an idle vertical well that has been shut in due to high WC and low productivity. Prior to drilling the laterals, a deviated pilot hole was drilled across the entire reservoir which helped optimize placement of the laterals. Reentry of an existing well to successfully steer and drill three long horizontal open drain holes into the reservoir imposed several constraints and added to the list of challenges.Incorporating sand control in a multi-lateral environment poses a number of challenges, with complexity driven by the Technology Advancement Multilateral (TAML) level demanded for the junctions between the motherbore and laterals, and by overall well functionality required. Well completion involved installation of an expandable sand screen (ESS) completion in the mainbore and Premium Sand Screens (PSS) completions in the two laterals to facilitate sand-free commingled production from all three laterals. The PSS completions featured a wash-down capability in the high-build angle laterals and also incorporated swell packers positioned just inside the laterals to ensure sand-tight conditions at the TAML Level 3 junctions. Following installation of upper ESP completion, a post-rig extensive clean-up program was conducted to unload all three laterals. The well is currently producing sand-free oil at three times the rate of neighboring single-lateral wells. Following the success and capturing the lesson learned from this trial, another ML well will be drilled in the field.
Over the last 10 years, matrix stimulation of multilateral wells has been one of the most fascinating and technology-driven interventions in the oil and gas industry due to the several challenges involved in this kind of operation. Overcoming these challenges, which include lateral identification and accessibility, reservoir assessment, and accurate placement of stimulation fluids, has encouraged operators and manufacturing and service companies to develop innovative techniques and novel technologies. In Saudi Arabia, coiled tubing (CT) equipped with real-time downhole measurements and a multilateral identification tool (LIT) has been one of the most valuable technologies to enhance the interventions in multilateral wells. Initially, the ability to monitor real-time data enabled a more efficient operation of the LIT, as well as optimizing and properly placing the stimulation treatment fluids by avoiding the identified high-intake zones across each lateral. Most recently, the incorporation of gamma ray tool into the real-time downhole measurements package allowed a faster identification of each lateral and accurate depth correlation for pinpoint acid stimulation; nevertheless, when this technology was deployed, pumping rates were significantly limited to a maximum of 2.0 bbl/min due to limitations on downhole tools and optical fiber installed inside the 2 3/8-in. CT. In some cases, this barrier also represented a drawback for optimum fluid penetration and efficient diversion across the zone of interest during the stimulation treatment. This paper documents the first worldwide applications of the enhanced version of a real-time downhole measurements package deployed on 2 3/8-in. CT for the successful matrix stimulation of a multilateral power injector well in Saudi Arabia, where the barrier of 2.0 bbl/min was far exceeded while maintaining intact all downhole readings. The operation represented a significant increase in operational efficiency and set a new record for this technology. A total of 4,585 bbl of stimulation fluids were injected across the open hole laterals (7,685-ft combined on both wells) at maximum rate achieved of 4.6 bbl/min, which were successfully accessed with the use of the LIT in a single run without the need to pull out the CT to surface. The use of enhanced the real-time downhole measurements package reduced the operational time by almost 50%, enabled more effective formation damage removal by injecting stimulation fluids at a higher rate, provided real-time depth correlation, verified access via gamma ray to each lateral without the need to tag total depth, and resulted in a tangible cost reduction.
This paper is a case history of two successful applications of mesophase technology for wellbore cleanouts and flow back enhancement. The first application was as a remedial treatment after the well's ESP pumped off and the second application was part of the completion process. Both wells were completed as open-hole horizontal wells, one with expandable sand screens (ESS) and the other with stand alone mesh type premium screens (SAS). Wells in this field are typically drilled with 65 pcf invert oil emulsion drill-in fluid (DIF) and can be as much as 800 psi over balance to formation pressure. The DIF is intuitively managed with respect to mud solids control, so there is no actual QA/QC on the solids management. The ESS completion was treated remedially with coiled tubing (CT) and rotating jet blasters months after the completion. The horizontal well was accessed through a Y-tool bypass that was part of the ESP completion. The SAS completion was treated with CT and rotating jet blasters after running the screen and setting the packer; prior to running the ESP completion, due to casing size limitations for running a Y-tool bypass. Introduction Despite increased emphasis on reduced drilling and production costs, attaining the maximum sustainable production of oil and gas wells is still critical to their economic development and optimized recovery. Productivity impairments associated with the fundamental mechanisms of near wellbore formation damage associated with drilling and completion fluids are well investigated and established.1 These near wellbore impairments are further exacerbated in open-hole completions, where a reduction in permeability can have a substantial impact on well productivity. In principle, minimizing the formation of an internal filtercake by appropriately selecting a sized weighting agent to bridge across the formation pores to prevent spurt loss should abate this reduction in permeability; however, in the field, the continual mechanical and fluid erosion of the external filter cake makes minimizing spurt loss and formation of an internal filtercake virtually impossible.2 Eliminating or reducing the effects of skin damage associated with drilling and completion fluids before a well is produced is advantageous. We report here two successful applications of a mesophase technology that is designed to clean up oil-based mud (OBM) filter cakes and the associated near wellbore filtrate damage. The treatment was applied post production, remedial, in WELL-1 and pre-production, as part of the new well completion in WELL-2. The observations demonstrate that the advantages and productivity enhancement of cleaning up OBM DIF and its associated damage as part of the completion prior to production. Background Invert emulsion DIFs are commonly used in drilling the heterogeneous duning Unayzah sandstones due their drilling performance and reduced risk of formation damage associated with in-situ clay swelling. These wells were drilled with a 65 pcf invert emulsion OBM DIF that utilized sized calcium carbonate (CaCO3) for bridging of the formation pores (Fig. 1). After the wells were drilled to total depth (TD), the holes were swept with diesel, followed by a high viscosity pill, and displaced to solids-free oil based mud in preparation to running the sand screen completions. WELL-1 and WELL-2 were both open-hole (OH) completed with ESS and SAS, respectively. WELL-1 is a twice-sidetracked 1600' horizontal producer that initially produced at 1.4 MBFD. Within the first month the rate of production had precipitously fallen to 0.5 MBFD, at which point the ESP was chronically failing due to under load and subsequently shut-in pending remediation. The clean up of the previous laterals with mud acid systems proved unsuccessful.
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