The recovery of unconventional oil such as heavy oil is receiving great interest as the world oil demand is increasing along with relatively high oil prices. Producing such high viscosity oil is complex and challenging, which usually require thermal techniques. Thermal recovery methods are widely used to recover the heavy oil and bitumen basically by thermally reducing oil viscosity, improving the mobility ratio and enhancing the heavy oil displacement. In response to the recent effort of leveraging heavy oil and tar plays in Saudi Arabia, Saudi Aramco has launched a new thermochemical research program to tackle challenges associated with lowering oil viscosity to improve well productivity and the overall reservoir depletion efficiency. One of the promising new technologies is enabling in-situ steam generation by chemical reaction (EXO-Clean) to mobilize the low API crude oil or tar reserves. In this paper a new steam flooding methodology will be introduced and compared with existing technologies. Steam will be generated in-situ by chemical reactions, which will have better efficiency and lower cost compared to conventional steam injection methods. Simulation study, lab experiments, and field treatment showed great promises of the technology. The developed EXO-Clean treatment relates to in-situ steam generation to maximize heat delivery efficiency of steam into the reservoir and to minimize heat losses due to under and/or over burdens and non-producing areas. The treatment consists of injecting exothermic reaction-components that react downhole and generate in-situ steam and nitrogen gas. The generated in-situ steam and gas can be applied to recover deep heavy oil, and tight oil reservoirs, which cannot be recovered with traditional steam injection methods.
This paper highlights the difficulties and limitations encountered and the respective solutions proposed and executed during an acid stimulation campaign conducted on multiple offshore power water injector (PWI) and oil producer (OP) platforms in Saudi Arabia.The field development concept for a mature brown field in Saudi Arabia includes a water drive mechanism, having unique placement of both onshore and offshore peripheral water injector wells for reservoir pressure maintenance. This field has a major concentration of extended reach hydrocarbon wells in the region. The offshore portion of the field has 83 developed wells on 13 platforms, with their openhole production profile ranging from 3,000 to 9,000 ft.Post-drilling or -workover operations, acid stimulation is required to restore well productivity or injectivity affected by drilling mud damage. A heavy tar mat zone, which characterizes the field, adds to the relative complexity of the PWI wells, generating hard mixed deposit bridges. For optimum treatment, each well requires uniform acid stimulation with significant volumes of chemically inhibited and diverted acid to achieve uniform zonal coverage, which are placed through 2-in. coiled tubing (CT) to help protect the completion from corrosion. Based on multiple laboratory tests conducted by the operator, an optimized treatment gradient (gal/ft) was fixed for this campaign, corresponding to significantly large stimulation volumes of 1,700 to 5,100 bbl for PWIs and 1,500 to 4,500 bbl for OPs.Because of offshore platform weight and space confinement issues, a rigless intervention technique was used, with a stimulation vessel handling the chemical additives, acid, diesel, and water logistics, on-the-fly treatment fluid mixing, and pumping, while a self-propelled barge handled the CT unit with nitrogen lift pumping capability and return handling system.The successful combination of the CT intervention and stimulation vessel fluid handling system in this campaign resulted in greater than 300% improvement post-stimulation in terms of both injectivity and productivity, with wells averaging 5 to 6 days for execution. This paper includes case histories of wells that were successfully stimulated in this campaign. The multiple successes of this stimulation campaign imply that significantly large stimulation treatment volumes can be designed for a complex offshore environment.
In one Saudi Aramco offshore oil field, the formation fluids are being produced from different platforms and transported to one onshore gas-oil separation plant (GOSP) where the produced water is removed from the hydrocarbon stream. The produced water is injected back to highly permeable formations through disposal wells with no interruption. In this way, the water disposal system is an integral part of the hydrocarbon recovery system. A failure of one of the disposal wells could adversely affect oil production. Saudi Aramco petroleum engineers are placing more and more attention on water disposal wells as a higher volume of produced water from the increasing hydrocarbon production rates has to be disposed of continuously every day. The primary objective of surveillance on the disposal wells is to keep an extra disposal capacity for continuous oil production from the field and to precisely monitor the decline rate of the capacity of each disposal well. Areal sweep efficiency and pressure maintenance are not the surveillance scope for water disposal wells in our case. Few technical papers have been published that discuss the problems a water disposal system may have in a matured field and address issues such as surveillance of well performance and water quality, formation damage mechanisms, treatment and so forth. In this paper, the existing water disposal system in a matured offshore oilfield is briefly described and discussed with the surveillance of well performance and the quality disposal water, potential problems, and the evolution of the surveillance philosophy. The reasons why most disposal wells experienced severe injection decline are analyzed and discussed in detail. Historic treatments were summarized with actual outputs demonstrating" ineffective" treatments for the issues discussed. After several trial tests, one customized chemical treatment recipe was developed to effectively tackle the issues and actual well data is included showing the effectiveness of those treatments. A new surveillance strategy for better monitoring of well performance and the quality of "waste" fluid is also discussed in this paper. It can be concluded from our work that formation damage exists extensively in wastewater injection wells and that it greatly influences the performance of disposal wells. Any treatment for restoring the injection capacity of water disposal wells impaired by low quality water is expensive. Any successful treatment is rooted into the detailed analysis of the problems. Implementation of a proper surveillance program and appropriate processing of the injection fluid is also vitally important for wastewater management.
Non-metallic tubing manufactured from fiberglass have been around for decades, and for good reason with multiple physical advantages over carbon steel tubing. However, this has also came with certain physical constraints such as the type of tubing connections and material brittleness with resultant low-pressure ratings. This has restricted a more widespread use of the material, particularly for downhole applications. In recent years, extensive research and development has evolved to manufacture 100% non-metallic composite tubulars with increased mechanical strength combined with high performance machined threads. The development of non-metallic composite tubulars have been in progress for many years, obstacles to the manufacturing process to deliver a material that was suitable for downhole conditions were numerous. The fully non-metallic fiberglass tubular is manufactured with aromatic amine cured epoxy resin, which not only provides the required strength but also an effective resistance to the harsh downhole conditions. Deep water supply wells that provide water injection are ideal candidates for this technology. The material is corrosion resistant, lightweight, zero maintenance, extremely durable with a superior hydraulic performance over carbon steel. The challenges of using carbon steel tubulars in harsh water environments are well known, and can lead to premature failure of the completion. Such failure can result in flow circulation across the electrical submersible pump (ESP) eventually leading to pump failure due to excessive heat in the motor. Fiberglass lined carbon steel protects the inner part of the tubing but still leaves the external side exposed to the harsh environment. The next step in the evolution for tubulars exposed to harsh conditions is 100% non-metallic manufactured tubulars. A custom designed resin system and manufacturing process with precise winding angle patterns delivered this high strength and chemically stable product. These properties allow for a maximum running depth of 12,000 ft, a maximum working pressure of 2500 psi and an expected life expectancy in the 10's of years. The tubing joints have API specification composite machined threads and are made up similar to traditional carbon steel tubing but requiring less torque. The successful deployment of 100% non-metallic composite tubulars in ESP powered water supply wells is another step towards increased utilization of this technology. A review has been completed of the manufacturing process, flow assurance, design integrity improvements and economic analysis of the 100% non-metallic fiberglass tubular. This completion design ensures well integrity & prolongs the lifetime of the assets and is in-line with the adoption of circular economy practices, simultaneously providing cost effective solutions and ensuring continuous improvement.
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