Recent studies have estimated that oceans have naturally sequestrated, by dissolving and mixing with deep waters, about 40% of the anthropogenic CO 2 emitted since the start of the industrial revolution. Moreover, the International Maritime Organization has recently announced that storage of CO 2 under the seabed would be allowed starting in 2007. To date, almost all studies, simulations and technical papers concerning carbon sequestration have focused on storing supercritical CO 2 in deep saline aquifers or depleted oil and gas reservoirs. However, a critical limiting factor for such carbon sequestration is the need for proper physical trapping and the necessity for monitoring the upward migration due to buoyancy effects and mobility of supercritical CO 2 . Carbon sequestration in deepwater sub-seabed formations provides an attractive alternative.This paper presents a feasibility study of carbon sequestration in deepwater formations in the Gulf of Mexico with the existing technologies available in the offshore industry. We describe each step of the carbon capture and storage process and discuss the technical limitations when trying to capture CO 2 from industrial processes, transport it offshore via tanker, drill a CO 2 injector well and then, inject the CO 2 from floating facilities such as drill ships or semi-submersible vessels. Due to high pressures and low temperatures reigning at water depths deeper than 9,000 feet, the liquid CO 2 injected in the first few hundred feet of deposits will have a higher density than the surrounding formation pore-fluid and therefore will be buoyantly trapped. In addition, CO 2 hydrates that may form and fill up pore spaces will act as an additional trapping mechanism. Finally, at these great depths, the CO 2 that could leak will dissolve by reacting with ocean waters and forming mainly bicarbonate compounds.Because oceans cover about 70% of the Earth's surface with an average water depth of 12,500 feet, deepwater sub-seabed sequestration provides an enormous storage capacity to counteract increasing world consumption of fossil fuels. However, large time and space-scale simulations need to be performed to estimate the impact of the change in geochemistry in the deepwater seabed region. Also, the injection of liquid CO 2 will force and displace formation fluid into the seabed surface zone, which will change the ocean chemistry.
Because many fundamental questions concerning the dynamics of the Earth and itsstructure remain unanswered, the Integrated Ocean Drilling Program (IODP) hasrecently completed a feasibility study for drilling and coring a hole 500meters (1,640 feet) through the Mohorovicic seismic discontinuity into theupper mantle of the oceanic crust from three candidate locations in the PacificOcean (Cocos Plate, Baja California, and offshore Hawaii). The main challenges discussed in this paper are threefold. First, drilling withriser in ultra-deepwater environments with water depths around 4,000 meters(13,120 feet) which will set a new world record. Secondly, drilling and coringin very high temperature igneous rocks with bottom-hole temperatures that areestimated to be as high as 250°C (480°F). Finally, drilling and coring a verydeep hole with a total drilled and/or cored interval around 6,000 meters(19,685 feet) in the oceanic crust below the Pacific Ocean seafloor in order toreach the upper mantle which will constitute a major achievement for theworldwide scientific community. This paper presents detailed analyses and several discussions concerning marinedrilling riser options by first reviewing the capabilities of the current riserconfiguration that is onboard the IODP scientific drilling drill-ship Chikyuand then evaluating alternative designs such as titanium riser, hybridtitanium-steel riser, slim-riser and lighter buoyancy modules. Furthermore, thedeepwater subsea equipment, drill-pipe design, wellbore design, down-holetools, drilling fluids, circulating temperature, cementing methods and variousadvanced technologies that would be required for this type of operation arealso reviewed. In addition, operational time and cost estimations for differentscientific drilling cases are provided (borehole continuously cored to totaldepth, continuous cores only across the major lithologic and geophysicaltransition intervals, spot coring and when only the mantle section iscored). Finally, this study helps evaluate critical issues in terms of current andtrending technologies in oilfield and geothermal industries that need to beresolved before embarking upon such a challenging project. The results of thiswork show that drilling to the mantle is certainly feasible, and that there areexisting solutions to many of the technological challenges based on work beingdone in the oilfield, offshore and geothermal industries.
As compared to a well in a conventional gas reservoir, a well in a tight gas sand (TGS) reservoir will have a lower productivity index and a small drainage area. The economic risk involved in developing a TGS reservoir is much higher than the development of a conventional gas reservoir as the economics of developing most tight gas reservoirs borders on the margin of profitability. Therefore, it is important to select the appropriate drilling method and technology to drill a given TGS reservoir condition. In our review of the petroleum literature, we have found few papers that provide a logical method for selecting the best drilling method and technology for a given set of reservoir conditions. There are individual papers that discuss individual, successful field cases where specific drilling methods and technology seem to work for specific reservoirs. We have used many of these SPE papers to help define "best-practices" concerning the selection of drilling technologies and methods. We then developed logic to provide advice on the best drilling technologies and methods for specific reservoir conditions. In this paper, we will explain the logic we have developed for choosing drilling technologies and methods for drilling a TGS reservoir. For several years, we have been working on software we call TGS Advisor. TGS Advisor can be used to provide advice to engineers developing TGS reservoirs. The program can be described as an ‘Advisory System’. The user enters the known reservoir data and the program provides advice on how to drill, complete and stimulate the reservoir. We have combined knowledge from the petroleum literature and interviews with experts to build the TGS Advisory system. We evaluated the results of the advisory system with published case histories in the SPE literature. In this paper, we will describe how we have included the selection of appropriate drilling technologies and methods used to develop TGS Reservoirs.
Surveys from the U.S.G.S, notably, have recently re-assessed the Arctic Circle and its deepest parts. Geology-based probabilistic analyses have found that significant oil and natural gas reserves, about 25% of the world's undiscovered resources, may be held in the deep Arctic Alaska (Bird, 2008; Houseknecht et al, 2010). Such studies are of the utmost interest for developed and emerging countries to help them meeting their growing demand in fossil fuels. As of today, the bulk of investigations, projects and technical papers concerning drilling for arctic oil and natural gas resources, have concerned the onshore hydrocarbon accumulations or the near shore deposits (OTA, 1985; Bercha, 1984; Matskevitch 2006; MMS, 2008). However, when trying to access the arctic deeper waters, only a few structures are available today to drill in these polar environments. Offshore operations in the Arctic Ocean are essentially impacted by extremely cold weather temperatures yielding the presence of sea ice, icebergs, floes and long period of darkness. Nevertheless, deepwater drilling and production in the Arctic Ocean provides an attractive but extremely ambitious challenge for our industry. Because the U.S. Beaufort Sea has an average water depth of 3,240 ft, deepwater drilling provides an interesting and innovative option to develop enormous reserves of oil and natural gas. This paper presents a conceptual study for exploratory and development wells in the harsh deepwater arctic environment of the U.S. Beaufort Sea by using a modified and winterized drill-ship with ice strengthened material or an icebreaker converted into a drilling vessel. In addition, ice management is discussed, considering a fleet of at least two icebreaker vessels to guaranty station keeping in first year sea ice and multi-year sea ice environments in order to conduct year-round operations with the floater. Also, the drilling and production phases will be discussed even in presence of icebergs or large ice floes. Finally, the paper briefly covers environmental regulations and economics. The main goal of this study is to help the oil and gas industry breaking the last barrier in exploration drilling and production by proposing structures and facilities that will enable to operate year-round in both open water and permanently ice-covered waters of the Arctic Circle.
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