The disposal of exploration and production wastes through deep well injection has increased dramatically during the last seven years. Prior to that time, most injection wells were used almost exclusively for produced water and brine disposal. During this period, the injection of waste solids in slurried form has been accomplished through low, sub-fracture pressure injection, slurry fracture injection, annular injection and injection into salt caverns. All of these types of disposal have been permitted by the governing regulatory bodies and have operated with varying degrees of success, problems and environmental impact. The injection of E & P solid waste has been, and continues to be, driven by the changing regulatory climate and by the sociopolitical perception of the industry, its' past and present methods of waste management and projections of future impacts and regulations. As the search for hydrocarbons has shifted to the offshore, the regulations governing handling and disposal of all wastes has become more rigorous. Of particular impact to E & P waste handling is past and projected modifications to permits tied to the National Pollutant Discharge Elimination System (NPDES). The key word in the title is "elimination" and the industry looks to injection to handle the elimination of the discharge of generated wastes into surface waters. Each different injection technology has its' own set of issues relative to its' applicability to a particular situation. These include regulatory controls and limitations, engineering parameters and guidelines, disposal capacities available, potential environmental and safety issues and liabilities and the public and regulatory community perception of all of the above. The continually changing regulatory framework and its' interpretation within a given region or state affects the implementation of the different injection technologies, as well as their commercialization. Introduction During the last two decades, various forms of injection have been used in the oil and gas industries to achieve permanent disposal of exploration and production wastes. For the purpose of this paper, we will focus on the recent methods used to dispose of solid wastes generated during operations. The disposal by injection of "clean liquids" such as produced waters filtered to various standards, has been part of the industry for several decades. Injection of these solid wastes usually entails the slurrification of the solids following some degree of particle sizing tailored to the limitations of the targeted receiving formation and the process employed. Disposal operations target structures ranging from salt caverns to highly consolidated formations that are fractured to achieve transport, containment and isolation of the injected slurried wastes. Certainly the bulk of the solid wastes disposed of by injection have utilized slurry fracture injection (SFI) or sub-fracture pressure injection methods. All of the methods available have the same goal; the safe and permanent disposal of solid wastes such that they are placed below the surface and isolated from any environmentally sensitive receptor in order to eliminate or minimize long term liabilities associated with the waste.
This paper is based on a field implementation in the United States of a biological process for improving waterflood performance. The Activated Environment for Recovery Optimization ("AERO™") System is being developed by Glori in collaboration with Statoil and derives its roots from a microbial enhanced oil recovery technology developed and successfully implemented by Statoil offshore Norway. Unique among IOR technologies, AERO implementation requires virtually no capital investment and achieves high performance efficiencies at low operational cost. The simplicity of setup allows pilot project implementation creating a very low risk entry point for the operator. A pilot project was selected for a controlled investigation of the performance and impact. Robust testing was done in both water and oil phases prior to treatment, confirming the potential for improved sweep and conformance from the project. Subsequent implementation resulted in decreased water cut and increased oil recovery observable both at the wellhead and allocated pilot levels. This paper summarizes a rigorous analysis of the pilot project’s performance to date, concluding that the production improvement should be credited to the implementation of the AERO™ System.
A new model and numerical scheme are developed to study the effects of poro-elasticity and thermo-elasticity on borehole stability. The poro-thermo-mechanical model integrates the effects of both thermal and hydraulic diffusion in determining the effects of the drilling fluid and mud weight on the borehole system. Thermal diffusion into shale formations occurs quicker than hydraulic diffusion, thereby dominating pore pressure changes during early time. The thermal differential can affect shale stability in two ways:The differential-driven thermal diffusion induces additional pore pressure that adds to the poro-elastic stress change near wellbore.The thermal differential directly induces a change in rock stresses. Previous publications have adequately investigated and addressed the second of the two issues. The current work attempts to model and assess the impact of the first mechanism. In the model, thermal diffusion is coupled with hydraulic diffusion to obtain the pore pressure distribution reflecting the cumulative impact. The generated poro-elastic and thermo-elastic stresses are obtained by solving equilibrium equations utilizing superposition. A field case is included in this paper and shown that the thermo-elasticity adversely would affect the borehole stability. Introduction Over the past 20 years a large number of studies have been dedicated to understanding thermal impact on borehole stability. Detournay and Cheng [1] developed the poro-elastic, transient and plane-strain analytical solution for an isothermal case. Wang and Papamichos [2] extended the model for the non-isothermal condition by uncoupling the temperature and the thermally induced pore pressure. Xuli [3] developed a fully coupled thermo-poro-elasto-plastic model. The above methods employed a finite element model in achieving the solution. Yu, M.J. and Sharma, M [4], [5] incorporated the chemical effect in the decoupled thermo-poro-elastic model and applied an analytical solution. Both the numerical finite element and analytical methods have their disadvantages. The field equations are difficult to solve within the finite element framework. On the other hand, the analytical method is unstable and slow. In this paper, a new numerical model based on finite difference method is developed to simulate the stress changes during drilling of an inclined wellbore subjected to an anisotropic stress field and a non-isothermal condition. Poro-elastic, thermal poro-elastic, thermo-elastic stresses are evaluated and their effect on borehole stability is addressed in a field case.
Coalbed methane (CBM) wells usually are dewatered with sucker rod or progressive cavity pumps to reduce wellbore water levels, although not without problems. This paper describes high-volume artificial-lift technology that incorporates specifically designed gas-lift methods to dewater Black Warrior CBM wells. Gas lift provides improved well maintenance and production optimization by the use of conventional wireline service methods.
The quality of produced and discharged waters is of increasing concern as the quality of potable waters within many regions of the country becomes a critical issue. The impact of discharged waters on the downstream water quality, as well as the flora and fauna within a discharge zone, is dependent on the quality of the water ultimately released into a drainage basin from a treatment system. In many regions of the country, discharge permits are being re-evaluated and sometimes recalled due to the actual and/or perceived impact upon surface and subsurface waters, particularly those providing water utilized by the human population. This is in response to the U.S. EPA's determination that the best method for dealing with produced waters was reinjection. Faced with the loss water that supports thousands of acres of wetlands across Wyoming, the State petitioned EPA to add an "Agriculture and Wildlife" exemption to allow surface discharge within lands under its jurisdiction in compliance with the NPDES program. As such, the Wyoming DEQ and Marathon Oil Company entered into a test project to ascertain the effectiveness of passive systems to treat produced waters to the NPDES toxicity requirements. The engineering design and testing of such a system was addressed in this study. The work was performed by students and faculty in the Environmental Science and Engineering and Petroleum Engineering departments at the Colorado School of Mines. The system consists of two surface flow cell units, one graded and one terraced, along with a constructed wetlands unit. These units can be independently evaluated. Untreated produced waters are presently being discharged into the drainage basin along with the diverted and treated waters. The system has been operational since July 1991. Initial results have been very promising and mechanical, chemical, and biological treatment in the surface flow and wetland units appear to significantly reduce the existing sulfide problem, as well as the released radium concentration. These are the constituents of major concern, although assays were also carried out for other parameters, including hydrocarbon content. Introduction In 1987, the U.S. Environmental Protection Agency (EPA) determined that the best practicable treatment (BPT) for produced waters was reinjection. For large operations with reinjection facilities this might not be a problem. However, for smaller producers the expense of hauling the water to a injection facility can often make the difference between profit and loss. In addition, the surface discharge of produced waters in the arid west support extensive wetlands that have become important habitat for mammals and migratory birds. After protest from producing western states, the EPA added an "Agriculture and Wildlife" subpart to allow surface discharge west of the 98th meridian in compliance with the National Pollution Discharge Elimination System (NPDES) of the Federal Water Pollution Control Act and amendments (33 U.S.C.A.).
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