Over the past decade, petroleum operators have shown increased interest in exploring and developing oil and gas reservoirs in both onshore and offshore Arctic areas. In many cases, the reservoirs are known to be overlain by massive permafrost layers on the order of 50 to 700 m thick. These conditions create unique design and operation challenges for production and injection wells from the perspective of ensuring that well integrity will not be compromised by the inevitable thaw subsidence of the permafrost soil layers. This paper presents a methodology for modeling and analyzing the severe casing loading and deformation conditions that can occur under thaw subsidence loading. The well design and evaluation methodology includes several sequential steps as follows: wellbore hydraulic and heat transfer analysis, to determine the heat input to the permafrost interval along the well(s) due to either the production of hydrocarbons or water injection; geothermal and geomechanical analyses, to calculate the extent of the permafrost thaw and the resultant thaw-induced soil stresses and movements; and casing-formation interaction analyses, to establish the structural response and evaluate the mechanical and hydraulic integrity of the well casing under the thaw subsidence loads. Sequential thermal and displacement analysis models are used to establish the extent of the thaw boundary that develops with time around the well(s) and the associated thaw subsidence response of the individual soil layers. These results serve as inputs to the non-linear analyses used to assess casing integrity. Examples are used to demonstrate the potential for thaw subsidence movements to cause casing failures, as a result of excessive compressive strains, buckling or large lateral deformations, in both single and multiple well layout scenarios. The methodology presented is recommended for optimizing well completion designs to minimize the potential for such failures to occur.

Progressing cavity pumps (PCPs) have proven to be a successful and reliable artificial lift system for production of heavy oil reservoirs over the past few decades. The application of PCP technology for production of oil wells in general continues to expand rapidly due to ongoing advances in versatility, production rate and lift capacity, durability, and economy. As a result, the application envelope for PCP systems has grown substantially to the point where these systems now successfully compete in many areas that were traditionally reserved to Rod Pump and ESP technologies. The development and implementation of a new type of PCP, namely the "all metal" (non-elastomeric) progressing cavity pump has been driven by the need to achieve significant improvements in the performance and run life of PCPs in high temperature/thermal well applications, and wells producing fluids which cause rapid chemical and/or mechanical degradation of elastomeric PCPs. This paper describes the successful implementation and use of Metal PCP systems in a diverse range of extra heavy oil wells located along the northern coast of Cuba beginning in July 2005. This is believed to be the first major use of this technology in such a field application. The paper also compares the performance and run lives achieved with the Metal PCPs to that of elastomeric PCPs in the same application. In general, the field trial results have demonstrated that the strong resistance of Metal PCPs to chemical and mechanical degradation makes them a good alternative for the cold production of heavy and extra heavy oil with relatively high bottomhole temperatures and high aromatic, CO2 or H2S concentrations. Introduction Progressing cavity pumps (PCPs), first developed and patented by Rene Moineau (Moineau, 1931), have found numerous applications in many industries as a means to efficiently transfer, transport and/or lift fluids of a diverse nature. The use of PCPs as an artificial lift method for oil wells has gained increasing acceptance since their first commercial use in heavy oil applications in the 1980's, and they have now become the lift method of choice in numerous oil field developments worldwide (Doval et al, 2007). This paper describes the use of PCP systems to produce extra heavy oil from a number of extended reach horizontal wells located along the northern coast of Cuba. The field experience includes numerous conventional (elastomeric) PCP installations over the past 8 years, as well as the deployment of several recently developed "all metal" PCPs beginning in July 2005 - this is believed to be the first major use of this new technology in such a primary production application. Relevant field data has been collected and analyzed to assess and compare the performance and service life of the various conventional and all metal PCPs.

Oil and gas producers have shown renewed interest in developing reservoirs located both onshore and offshore within the Arctic regions of Alaska, Canada and Russia. In many cases, the hydrocarbon reservoirs are known to be overlain by a massive permafrost interval that extends over depths of up to 700 m below the surface active layer. These conditions create unique design and operational challenges for production and injection wells from the perspective of ensuring that well integrity will not be compromised by the inevitable thaw subsidence of the permafrost soil layers.The permafrost soil layers surrounding arctic wells will thaw gradually with time due to wellbore heat loss. As the thaw zone advances radially outward from each well, the ice-to-water phase change within the pore space of the frozen/partially frozen sediments will lead to changes in the permafrost soil properties and to the loading conditions within the thaw column region. These changes will result in soil deformations (including both vertical settlements (subsidence) and horizontal displacements) which can, in turn, induce significant well casing strains that need to be considered in selecting the well design and layout. The magnitude of the soil deformations that occur throughout the permafrost interval are highly dependent on the deposition history, insitu temperature and the physical and mechanical properties of the individual soil layers. Therefore, in order to accurately predict the soil deformations and resultant localized casing strain levels, it is essential to obtain reliable data to properly characterize the lithology (soil types) within the permafrost interval, as well as the frozen state and the relevant mechanical and thermal properties (both frozen and thawed) of individual soil layers. This paper describes the various information and geotechnical test data that has been used to establish the thaw and deformation response of different permafrost soils at a number of arctic locations for the purpose of evaluating the effects of thaw subsidence loading on wells.Overall, the paper serves to highlight the importance of collecting the appropriate geotechnical data to allow thaw subsidence-induced ground deformations and associated casing loading conditions to be properly considered at the well/project design stage. 2 OTC 23747irreversible ground movements throughout the thawed soil column in the vicinity of production wells. The thaw and deformation response is highly dependent on the permafrost lithology and soil properties at each particular location and it is important to recognize that these conditions can differ considerably even within relatively small geographic areas. This paper outlines the key factors which influence thaw subsidence potential and describes the various information and geotechnical test data that has been used to establish the thaw and deformation response of different permafrost soils (e.g. coarse-grained and fine-grained) at a number of arctic locations for the purpose of evaluating the effects of thaw subsid...

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