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Polymer gels have been effectively applied to extend the productive life of mature oilfields by mitigating water production and enabling the recovery of bypassed oil reserves. A key component for a successful conformance improvement treatment is the identification of the most appropriate gel technology for a targeted reservoir. Gel projects are capital sensitive and involve high degree of risk; therefore, it is crucial to select a proper gel technology and provide an optimized design project. This paper presents the first generalized comprehensive selection system for injection well gel technologies based on the comparative analyses of the characteristics of conformance problems in gel field projects. 111 field trials of three in-situ gel systems including bulk gels, colloidal dispersion gels, and weak gels were summarized from 1978 to 2015. First, reservoir/fluids characteristics, diagnosis indicators used in the evaluation of drive-fluid channeling strength, and treatment operational parameters were summarized. Then, problem zone volumes were estimated using a design rule of thumb and the problem development status was indicated using some production-related parameters. Finally, all characteristics of conformance problems were compared for different gel systems to identify factors implicitly used in the nomination of gel technologies in the field projects. We recognized that gel selection process starts by matching characteristics of conformance problems with technical specifications and mechanisms of the gel systems. Then, the initial candidate technology is confirmed by screening criteria to ensure gel system compatibilities with reservoir and injected fluids. We identified that the most influential characteristics in the selection process are drive-fluid channeling strength, volume of problem zone, problem development status, existence of cross-flow, and the nature of the required solution whether it depends on gel strength or volume. It was recognized that the existence of crossflow or high oil saturation in the offending zones turns a limited conformance problem into a large volume issue that needs the application of the flood-size treating technologies. For these situations, current oil saturation in the problem zones is the key factor rather than oil saturation in the less conductive zones because it is guaranteed by the high reservoir permeability heterogeneities. In addition, the problem development status does not only affect the selection of a gel system, but also its design parameters such as polymer concentration. The novelty of the new gel selection system is in its utilization of standardized general parameters and provision of distinct parameter cut-offs for each gel technology.

The study presented here examined a Kuwaiti reservoir that is classified as a next-generation extreme heavy oil tar-mat reservoir. Successful pyrolysis experiments were performed on carbonate rock containing 33.51% total organic content (TOC). Comparable toluene solvent, water extraction, and surfactant solution extraction had successful but different hydrocarbon recovery yields under different temperature settings. The tar-mat flow was extremely viscous, with a measured "API density close to 1.34 and calculated flow mobility close to zero. Depending on the type of extracting agent applied, increasing the temperature cracked the extreme heavy oil tar-mat available in the carbonate rock, hence improving the extremely viscous nature of the solid residue and causing it to be mobile so that it could flow and be recovered. Four carbon-density flow regimes were identified in this extreme heavy oil tar-mat composition mix, including the free hydrocarbon type I composition (C1–C15), the light hydrocarbon type II composition (C15–C40), the heavy hydrocarbon type III composition (>C40), and the insoluble carbon-residue type IV material (NSO). Each flow regime exhibited a unique recovery potential within the extremely viscous composition mix. A detailed characterization of this tar-mat sample confirmed that the release of trapped type I, type II, and type III compositions from the carbonate pore space was possible, while type IV residue remained resistant to flow, and hydrocarbon retention on the rock was difficult to overcome with the suggested recovery treatments.

Abstract The Government of the Republic of Trinidad and Tobago has embarked on a major energy sector project to recover proven reserves of crude oil contained in onshore and offshore producing fields, using secondary recovery techniques. Onshore reserves of crude oil are produced using steam flooding techniques while offshore reserves are recovered through water injection techniques. These projects are being undertaken by Petrotrin and Trinmar Limited respectively. An Environmental Impact Assessment (EIA) conducted prior to the start of the projects served to identify key environmental sensitivities associated with each project. Environmental Management Strategies were developed by both Companies to mitigate against the potential impacts of each project and are in various stages of implementation. These include: The establishment of Environmental Units, the conduct of employees training programmes, the implementation of preventative maintenance programmes, the introduction of new oily wastewater treatment facilities, application of environmentally acceptable solid waste disposal methods, regular monitoring of effluent quality, ensuring compliance with interim Company Standards and the development of oil spill contingency plans. In addition, Petrotrin has begun a groundwater quality monitoring programme, a rationalization programme for storage facilities and adopted and implemented various components of ARPEL's environmental guidelines. Additional strategies implemented by TRINMAR Limited include risk analysis for submarine pipelines, a gas emission control programme and the conduct of annual Environmental Audits. Environmental Management Act, 1995 which provides for the establishment and operation of an Environmental Management Authority, has just been enacted. However the enforcement of environmental legislation has been hampered by the lack of coherent effluent standards and regulatory agencies. The onus for managing the environmental impacts of the projects undertaken therefore lie within the respective Companies. The extent to which this is done is largely due to their management's commitment to achieving acceptable levels of environmental performance. The Environmental Management Strategies adopted by both Companies ensure that activities associated with the projects comply with their respective corporate missions and environmental policy statements. Introduction The Government of the Republic of Trinidad and Tobago has embarked on a major energy sector project to recover proven reserves of forty-four (44) million barrels of heavy oil from onshore and offshore producing fields. This project is being principally funded by a loan obtained from the Inter-American Development Bank, the funds from which have been made available to the Petroleum Company of Trinidad and Tobago Limited (Petrotrin) and Trinmar Limited. Trinmar is a consortium of Petrotrin and Texaco Trinidad Inc. The Enhanced Oil Recovery Project is implemented as two (2) Sub-projects. Sub-project A addresses the secondary recovery of heavy oil from land based production fields (Forest Reserve Field and Cruse E Field expansion) using steam injection techniques and the transfer of recovered crude to the Pointe-a-Pierre Refinery and is being implemented by Petrotrin. Sub-project B involves the secondary recovery of medium density crude from an offshore producing field (Soldado Main Field) using water injection techniques and is being implemented by Trinmar Limited. (See Figure 1). P. 485