The High-Tech World of Testing

Mario Ruscev, President, Testing Services, Schlumberger

Driven by mounting pressure to reduce E&P risk, the testing techniques introduced by brothers E.C. and M.O. Johns-ton in the 1920s are mounting a revival. But they bear little resemblance to those early days when simple downhole tools were run and the only measurements consisted of examining the produced fluids. Often characterized by large amounts of piping and heavy equipment, testing has become high-tech and makes use of the most sophisticated types of metrology available. Today, testing results can be delivered in near-real time. Results are highly accurate and integrate seamlessly with comprehensive, dynamic reservoir models that benefit from the aggregate of exploration, drilling, formation evaluation, and production data.

In reality, a test involves a pressure sensor of the right resolution and accuracy put in the right place and left for the right amount of time. The trick, of course, is in the determination of what is “right,” and that involves a deep under-standing of the reservoir as well as flow dynamics and fluid mechanics. Absent these qualities, a test can be deemed a “successful failure”—meaning one where all the valves, chokes, separators, tanks, and gauges work properly, but the data are ambiguous and inconclusive.

Today, operators simply cannot risk getting it wrong. For example, if a subsea system or a floating production facility is installed that is either too large or too small or because production was incorrectly predicted, the cost can be ruinous. The risks of drilling and completing wells have grown exponentially, as have the potential values of oil and gas production. Modern testing minimizes those risks to the maximum.

Plumbers No More

While hooking up myriad valves, pipes, and tanks to separate fluids into three phases (oil, gas, and water) in order to make flow measurements worked in earlier times, it cannot solve today’s challenges. In the past, the industry’s appreciation of testing was gauged by the amount of steel involved. Today, high-speed sensors resolve multiphase flow that often includes gas and condensate. Operators need solid information on which to base critical decisions, and they want details on today’s well conditions, as well as an accurate view of the future. Answers must address life-of-the-reservoir issues. Much of the technology to support these solutions is available, but more development is needed. Two areas in which high technology is playing a major role are multiphase flowmetering and fast pressure/volume/temperature (PVT) analysis.

Portable on-site well fluid analysis services are now available that can be set up at the wellsite in minutes and provide key fluid parameters that figure in the operator’s production decisions. Essential for evaluating the profitability of the prospect, fluid composition and physical properties from samples collected at the wellhead impact completion and production facility design. Compositional analysis to C12 for gas and C36 for oil provides key input for reservoir and equations-of-state simulators. Results can now be derived, verified, and presented, usually before the testing crew has rigged down. Besides enabling near real-time-quality control, data from the on-site PVT analysis are used to optimize multiphase flowmeter measurements.

New Horizons

Testing has found an important application in heavy-oil regions. With half the world’s largest developments seeking to produce heavy crude, new testing technology is needed to develop systems that can accurately meter the complex multiphase flows that result from heavy oil production. Multiphase metrology can sort out the combinations of oil, condensed steam, and solvents to provide more representative flow-rate and holdup answers and to help operators better define such parameters as viscosity and composition to solve the economic viability puzzle.

Once confined to evaluation of new or appraisal wells, testing has found an important new role in cleanup activities following well completion, intervention, or stimulation. Conventionally, wells are not put through a test spread until the fluid is relatively clean, making estimates of returned drilling and completion fluids difficult. Multiphase metering now enables monitoring of the entire cleanup process. Using a multiphase testing service, well effluent measurements are made from the initial opening of the well. Well cleanup takes the least time possible, and lifting costs are minimized. Because results are accurate and available in near-real time, operators can measure the effectiveness of treatments of workovers while equipment is still on site to perform remedial work if necessary to ensure that expectations are met. And today’s large investments in challenging environments, such as deep water, call for “insurance” that a reservoir’s potential is known accurately for its projected economic life before investments are made in production facilities.

Knowledge Is Power

In addition to making great strides in technology, the human factor has not been overlooked. Many more formally trained and experienced reservoir engineers are joining the field force. They form a strong resource base to collaborate with the operator’s engineers in every phase of the testing operation, from design through implementation to interpretation and analysis. A result of these staff additions has been expansion of production-testing capabilities. This is what modern testing is all about—measurement, understanding, applied reservoir engineering, and putting it all into a program that gives better reserves calculations, producibility, how the reservoir will produce, rate, volume, and composition.

Some believe that testing is reserved for giant offshore fields where investment and risk is high. However, Saudi Aramco, with its
e-Field concept, has proved that profits of land operations can be vastly improved through the judicious use of testing. Some of the applications currently addressed by testing include reserves calculations, accurate resolution of complex flow regimes, permanent well and reservoir monitoring, production allocation, and dynamic optimization.

Testing will play an increasing role in solving long-term production challenges. However, the solution will require a coordinated industrywide effort to provide opportunities in which new technology and techniques can be evaluated. With demand at an all-time high and supported by strong market forces, the time to do this is now. Among the key benefits provided by today’s technology are high turnaround rates of accurate, reliable information from data that formerly took weeks or even months to interpret. And improved safety and environmental protection have resulted from the reduction of complex, bulky equipment setups and reduced gas flaring. In a world where failure is not an option, testing minimizes risk.

Mario Ruscev is President, Testing Services, for Schlumberger, a position he assumed in May 2006. Located in Paris, he directs the global activities of Schlumberger’s testing services, including product development programs. Before assuming his current role, Ruscev was president of Schlumberger Water Services. Prior to that appointment, he held the position of president of Wireline and he also served as president of Geco Prakla. Ruscev began his career at Schlumberger in 1984 in the company’s nuclear team in Montrouge, France. Prior to his executive appointments, he served in positions of increasing responsibilities in research, engineering, and manufacturing. Ruscev earned PhD degrees in nuclear physics from Yale University and Université Pierre et Marie Curie in Paris.