Drilling Kerr-McGee's deepest development to date in the Gulf of Mexico.
Toward Energy Independence
August / September 2004
Volume 2 Number 4
Concerns about U.S. dependence on foreign oil are nothing new. Unsettled conditions in the Middle East, America's prime outside supplier of petroleum, have existed for decades. U.S. administrations have responded to the threat to the foreign supply pipeline by attempting to steady the political climate in the oil-rich nations. They prime the domestic pump with efforts to open up hitherto protected regions for development and with funding support for fossil energy R&D. The latter is an area where the government's legislative, administrative and financial clout could bring America closer to energy independence without incurring the resistance of foreign powers or the outrage of U.S. citizens who believe that drilling rigs don't belong in wildlife refuges.
One government-sponsored program, the Department of Energy's Natural Gas and Oil Technology Partnership, promotes technology transfer from the national laboratories to the oil and gas producers. The collaborative R&D projects in this program could slow the rate of increasing dependence on foreign oil by applying expertise in modeling and simulation, materials, sensors and systems engineering to help increase the efficiency of extraction processes for oil and gas from domestic reserves.
Linking Labs, Oil and Gas Producers
In 1988, DOE established the Natural Gas and Oil Technology Partnership (NGOTP) to bring together the expertise of the national labs in collaborative projects with the nation's oil and gas producers and service companies. Universities and other research institutions are also members of project teams. The industry-driven program established review panels and forums that define industry needs, provide annual project reviews, and determine the priority of new proposals and ongoing projects. Currently, in addition to the 9 national labs, the partnership includes 9 major oil and gas companies, 10 independent producers, 45 service companies, and 12 universities. With the goals of producing more oil and gas from domestic reservoirs while safeguarding the environment and working within today's economic constraints, the NGOTP is currently fielding around 40 projects that explore the range of technological innovation throughout the research-development-application curve in a number of areas, including oil and gas recovery; well drilling, completion, and simulation; and environmental protection.
The industry calls on the lab's expertise in scientific computing and geomechanics to help it develop new technologies for managing the interactions between fluids and solids near the wellbore, the below-ground column through which the drilling tools pass and the oil or gas is brought to the surface. The Direct Simulation of Near-Wellbore Mechanics project joins Sandia with the Massachusetts Institute of Technology, the University of Wisconsin at Madison, BP, ChevronTexaco, ConocoPhillips, Halliburton, Schlumberger, and Shell to develop computational capabilities that can be used by the industry to understand processes in the near-wellbore region. These processes commonly must cope with sand in the well fluid, which erodes casings, pipes, or pumps, or even plugs the well. Procedures, such as hydraulic fracturing (the pumping of fluid under high pressure into the reservoir rock to create openings and increase the flow of oil or gas), or proppant transport, where particles are deliberately mixed with the fracturing fluid to hold fractures open after a hydraulic fracturing treatment, also create extremely difficult environments in which to operate.
Until recently, the understanding of these processes and the ability to predict the behavior of the materials near the wellbore has relied on computer modeling approaches that generalize the interactions between fluids and solids or on difficult-to-perform and expensive experimental studies. In this project, Sandia and its partners have developed 2-D and 3-D coupled (fluid and solid) computer models for the high-fidelity simulation of near-wellbore mechanics. These models illustrate the interaction of individual solid particles (and cemented particle assemblies) with other solid particles and with the surrounding oil or water.
With guidance from the project's industry partners, the model is now being applied at Sandia to simulate sand production from an idealized wellbore region to better understand the fundamental parameters, like the shape of sand grains and the stress-state of formations, that govern sanding and stabilizing mechanisms in the field. According to Sandia project leader Ben Cook, "These results can ultimately be used by industry to better predict the likelihood of sand production and to engineer new mitigating controls, economically necessary advancements for many potential oil-producing fields that are considered marginal prospects today because of sand-related problems."
Deepwater Drilling
Sandia is also applying its capabilities in computational geomechanics to facilitate the oil and gas industry's push into the deepwater Gulf of Mexico, regarded by many as the U.S.'s last great fossil energy exploration and production frontier. In the Well Integrity Assurance for Sub-Salt and Near-Salt Deepwater Gulf of Mexico Reservoirs project, co-funded by DOE and the industry partners, Sandia is teaming with BHP Billiton, BP America, ChevronTexaco, ConocoPhillips, ExxonMobil, Kerr-McGee, Petrobras S. A. and Shell to investigate the influence that overlying and adjacent undersea salt structures have on the development and production of deepwater Gulf of Mexico reservoirs.
The Gulf of Mexico is the most active fossil fuel-producing deepwater region in the world and is estimated to contain undiscovered recoverable resources of nearly 30 billion barrels of oil. By next year, as much as 67 percent of the daily oil production and 26 percent of the daily gas production in the Gulf of Mexico will come from deepwater fields. Complicating the recovery of these resources are huge formations of salt, thousands of feet thick, that underlie much of the deepwater. The complex salt tectonics, coupled with extremely deep water (up to 10,000 feet) and a reservoir up to 20,000 feet below the sea floor, require high development costs and innovative technologies to bring these fields on stream.
The cost of drilling these deepwater wells ranges from $25—€“$50 million per well and drilling failures adjacent to salt formations have resulted in well abandonment costs of tens of millions of dollars. Wells may collapse during drilling because of the changing stresses of salt deformation. Even after a well is cased and completed, the slow movement of salt over the field lifetime may cause premature failure of the casing through shearing and twisting. Bernard Loony, BP America's drilling team leader for the Gulf of Mexico/Thunder Horse well team, says Sandia's work led to $30 million in savings in well construction costs at the Thunder Horse field. "By working with [Sandia] on salt mobility, we have identified ways of positively impacting the project economics and delivering a more reliable solution. To me, this epitomizes the manner in which government agencies and industry can collaborate to produce extraordinary results."
This project is using Sandia's nonlinear finite element geomechanical computer modeling to investigate the stresses associated with salt formations and the forces that subsurface salt formations exert on well casings, with the goal of developing technologies to counter the effects of salt deformation.
Complementing the computer modeling, laboratory-based rock mechanics experiments have been conducted to understand the behavior of Gulf of Mexico salts.
Reservoir-scale computer models help researchers understand and predict the complex geomechanics of drilling and production through or next to salt formations and to identify optimal well trajectories and locations of potential borehole instability.
According to Joanne Fredrich, Sandia's principal investigator, the project "targets an area of strategic importance to the industry, and is an excellent example of where our capabilities are exactly those needed to address key technical issues associated with developing these deepwater fields that are so critical to the nation's energy security. Besides the ongoing work under this project, we are also actively working geomechanics-related issues for various partners."
Solving the Sucker Rod Problems
Another Sandia effort for the NGOTP is Measuring Sucker Rod Pump Parameters Downhole, a project with Harbison-Fisher and the University of Texas at Austin.
Sucker rods are steel rods that make up the mechanical assembly between the surface and downhole components of a rod pumping system. Sucker rods are 25 to 30 feet long and are threaded at each end to enable the downhole components to be inserted and retrieved easily. Although sucker rod pumps are installed in nearly 90 percent of all oil wells in the U. S. and have been widely used for decades, many issues regarding their use are not well understood. Persistent problems in sucker rod pumping, which are difficult to diagnose from the surface, lead to reduced production and increased equipment failure.
This project developed an instrumented downhole pump to directly measure conditions inside the pump while it is stroking under wellbore conditions. A full-scale transparent pump, constructed and installed at the University of Texas at Austin, was instrumented with pressure gauges to measure the pressure profile throughout the pump while it is stroking. The transparent pump and fluids allow visual measurements and observations to be made to confirm the instrument readings. Tests were conducted of the pressures and loads in the pump under a variety of fluid and pumping conditions. Based on the experience gained in instrumenting the laboratory pump, as well as previous experience with the downhole tools, the instrumented pump was modified for use in an actual wellbore at reservoir temperatures and pressures.
The deployment phase of the project is currently on hold due to a funding pull-back. If the project continues, the pump will be deployed in several wells and tested under a variety of pumping conditions. ARCO and other oil field operators will make the wells available and provide field test support. The data resulting from the tests will be widely distributed to the industry.
Ample Supplies, But Hard to Reach
Chip Mansure, Sandia's project lead for the sucker rod investigation, believes that the NGOTP program is making a contribution to energy conservation. "For each reservoir tapped, the benefit in oil and gas produced should be maximized and the environmental impact minimized. For example, for the stripper wells, wells that make less than 10 barrels per day, which include the vast majority of old U.S. oil wells, most of the environmental impact was already paid up front when the wells were drilled. What remains to be done is maximizing the ultimate recovery while minimizing the incremental environmental impact."
While oil and gas are not in any practical sense renewable resources, according to the NGOTP approximately two-thirds of the oil-in-place in the continental United States remains in the ground—€”more than 300 billion barrels—€”and natural gas offers a secure, abundant, clean energy source. Advanced technologies are needed to economically produce more oil and gas from these domestic reservoirs while protecting the environment.
Margaret Lovell is a writer at Technically Write assigned to Sandia National Laboratories.
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