Extreme Drilling Laboratory Is Ready to “Rock and Roll”

	The Extreme Drilling Laboratory is located at the NETL Morgantown site. Initial research operations will begin in 2010.

The Extreme Drilling Laboratory (XDL) at the National Energy Technology Laboratory (NETL) proudly announces the much-anticipated debut of its prototype Ultra-deep Drilling Simulator (UDS), the rock star of the XDL. Drilling research will begin soon at an experimental well site with pressures reaching 30,000 pounds of force per square inch and temperatures exceeding 480 °F at the bottom of the well. One of the many unique features of this extreme drilling research is that 100 percent of the drilling will occur above ground. In addition, the UDS operating pressure and temperature ranges are three times greater than those found in similar drilling rigs and are representative of conditions found in ultra-deep wells, or wells with depths near 30,000 feet.

The concept of the high-tech facility located in Morgantown, W. Va., was conceived in cooperation with industry and funded by the Federal Government under Section 999 of the Energy Policy Act of 2005. Research conducted in the XDL is expected to have a direct impact on increasing our domestic supply of oil and natural gas (NG) by developing affordable, efficient, and environmentally safe means to harvest ultra-deep oil and NG resources.

The UDS will allow researchers to study the physical phenomenon of the cutter-to-rock interface, so they can explore and develop the technology required to efficiently drill rock at the high-pressure, high-temperature (HPHT) conditions found far below the earth’s surface. In addition to exploring the dynamic interaction between the rock cutter and the rock, XDL researchers will have at their disposal a state-of-the-art Drilling Fluids Lab (Mud Lab) and a Mineralogy, Modeling, and Materials Lab (Rock Lab). These supporting labs will provide the means to identify and analyze the singular aspects of rock properties and formations that can influence both the economic and operational processes of ultra-deep drilling.

Setting the XDL Stage
Oil and NG make up nearly 60 percent of our Nation’s energy consumption and are often found together in wells. There has been a significant decline in annual production rates in recent years. For example, the number of NG gas wells drilled in the Gulf of Mexico, one of the Nation’s most plentiful sources of oil and NG, declined from 1000 wells in 1997 to 300 wells in 2006. Even though new technologies can quicken resource production (thus shortening well life span), retrieving these vital energy resources is still difficult. Oil and NG stakeholders are required to develop innovative exploration and production technologies for increasingly challenging geologic environments, such as those found in ultra-deep wells far offshore.

Inside the pressure vessel is where the main action takes place. Extreme pressures up to 30,000 psi literally push the 6000-pound pressure vessel to the limit.

As the availability of drill rigs has decreased, research investments have also decreased while control of oil and NG production economics is now shifting to the world market. For example, resource exploration in the United States has now shifted to foreign resources that are more accessible and thus provide a higher return on investment. Costs for unconventional production methods such as deep-well drilling can be staggering. NETL’s Strategic Center for Natural Gas and Oil reports that drilling the last 10 percent of the hole can account for 50 percent of the drilling cost. Meaning, the deeper we go, the higher the costs. Through its high-tech equipment and advanced research, the XDL is hoping to optimize drilling methods and technologies that reduce the risk and cost of deep drilling.

It’s Rather Complicated
Drilling for oil is a complex process, and despite what is shown in the movies, “black gold” does not simply rush to the earth’s surface once the drill bit reaches the reservoir. First, the oil company drills down to rock formation containing the oil or NG—XDL will focus on this drilling step of the process. Then the well is completed, which includes tasks such as cementing the well casing in place and fitting the well with a wellhead to control flow. After well completion, gathering lines must be installed to route the oil and NG for further processing or to market.

During the entire drilling process, a special drilling fluid called “mud” is pumped continuously around the drill bit to minimize friction, cool and clean the drill bit, and carry the rock cuttings away from the cutting area and back to the surface. The column of mud places weight on the drill bit, enabling it to exert more crushing pressure on the rock. This “formation pressure” is similar to that created by the rock formations above the cutting depth and tends to compress the rock, making it stronger, and thereby increasing the energy required to drill the rock. The rock’s porosity (how much fluid its pores can contain) and permeability (its ability to transmit fluid) can also affect its mechanical properties and play an important role in the drilling process.

The majority of prospective deep wells are expected to be drilled offshore. Surprisingly, only 30 years ago, deep-water drilling referred to wells drilled hundreds of feet underwater. Today ultra-deepwater drilling can occur in water depths greater than 10,000 feet. This is a substantial increase in depth and goes hand in hand with significant increases in well pressures and temperatures. A phenomenal financial and physical effort is required for deep-water drilling, as drilling platforms can cost hundreds of millions of dollars and take up to 3 years to complete.

	The UDS is a unique research tool. Its rests on a massive load frame that makes it possible for the simulator to contain the extreme forces acting on both ends of the vessel.

Ultra-deep Drilling Simulator: The Star Player
The UDS is a remarkable research tool that will provide simulations of the drilling environments found at the bottom of deep wells. Deep wells often produce larger sustainable amounts of oil and NG than their shallower counterparts, but deep drilling also means higher pressures and higher temperatures that can impact the drilling rate of penetration and drive up costs. In the lab, advanced research will be conducted in real conditions and then applied in both the field and downhole.

The unassembled simulator was delivered to NETL in January 2009. There it was re-assembled by in-house researchers in a two-month-long process, and underwent a pressure check in April and May. After running a multitude of intricate instrumentation and system checks, researchers are now in the early stages of shakedown and baseline testing. The XDL is looking forward to the first quarter of 2010, when initial UDS research operations will finally begin.

Handling the Pressure Well
The UDS maintains pressures up to 30,000 psi and temperatures up to 480 °F through a computer control system. The UDS uses drilling fluid to exert the force needed to create HP conditions within a pressure vessel that is supported by a massive load frame. This load frame is what contains the tremendous thrust forces generated by the immense pressure acting on both ends of the vessel, while the massive 6-inch-thick walls of the pressure vessel effectively contain the longitudinal forces trying to expand them. At these extreme operating pressures and without this containment, the steel of a thinner-walled vessel would expand just as if one were blowing up a balloon.

The bottom plug is in the lower end of the pressure vessel and holds the test specimen, which is forced against the cutter assembly located in the top plug.

To provide a feel for the operating pressure of the UDS, consider that the human body can withstand as much as 400 psi of sustained pressure providing it is gradually increased to this amount. Next, compare UDS pressures to pressures measured in the deepest part of the world’s oceans, the Marianas Trench. At the bottom of the trench, where Earth’s tectonic plates meet, the water column above exerts a pressure of 15,750 psi, which is over 1000 times the standard atmospheric pressure at sea level and half of the USD operating pressure. Pressure in the trench would easily crush modern-day nuclear submarines made of the ultra-high-strength steel—just imagine the potential of the UDS.  

	The top picture is an actual photo of a cutter-rock interface. The bottom picture is a model of a cutter-rock interface simulated in the XDL Modeling and Simulation Lab.

This world-class prototype simulator basically consists of a pressure vessel, load frame, a control system, and ancillary equipment such as high-pressure pumps and hydraulics. The actual cutting of rock takes place within the pressure vessel. There the test specimen is mounted in the bottom of the pressure vessel to the bottom plug, which has been designed and fitted with a hydraulic motor and actuator. From here, the rock is rotated and forced against a stationary cutter assembly suspended from the top plug. The cutter assembly has been instrumented to precisely measure the amount of force created during the cutting process.

Diamonds are UDS’s Best Friend
The UDS’s primary type of cutter will be what the drilling industry terms as a PDC cutter. A PDC cutter is constructed of a steel disk—usually less than 1 inch in diameter and approximately less than 1 inch in length—coated with polycrystalline diamond, a synthetic diamond that has been metallurgically bonded to the steel. PDC cutters are excellent for the XDL’s purpose because they have a very high scratch hardness value and are extremely stable chemically.

CLICK ON IMAGE BELOW TO VIEW VIDEO
In this video [WMV-1.6MB] of the cutter-rock interface, the image is tilted 90 degrees to provide a better view of the cutting action. The cutter is on the left and the rock test specimen is on the right. Notice how the rock shears off and the particles scatter in various directions.

Taking a Look
In order to see what is going on inside the reaction chamber, NETL engineers are in the final stages of designing and installing two visualization systems. The first will take high-speed video through an observation port positioned to view the rock-to-cutter interface. This technology, called a high-speed particle imaging system, is already used at NETL to study millions of particles in a quick-moving liquid or gas stream. The UDS application will take this technology one step further by allowing scientists to view the interaction between cutter and rock, in slow motion, at full-system pressure using a clear drilling fluid. In the future, XDL researchers hope to use X-ray imaging to visualize the cutting action while operating with opaque drilling fluids. This will mark the first time the X-ray visualization concept is used in this application.

	Drilling mud looks much like regular mud, but its composition is anything but. It can be oil-based or water-based, the materials are carefully selected, and the composition is designed to best enhance the drilling process.

Mud, Rock, Modeling: The Supporting Players
The supporting labs complement the UDS and enhance the diversity of research conducted. The labs also provide the needed bridge to determine, explore, and correlate the physical and chemical properties of rocks, drilling muds, and rock formations. Once this data is assembled, researchers can develop the mathematical equations that will be used to predict and optimize the drilling process. XDL researchers have established the Mud Lab where they can mix and measure the properties of various mud “recipes” in an attempt to create the perfect mud for specific situations. Different drilling muds can have different impacts on the rock formations within the well, as well as the cutting process near the drill bit, including lubrication of the bit-rock interface and degradation of the rock.

The XDL Rock Lab was established to serve a variety of functions, from simple preparation of rock samples to detailed analyses of test specimens. In addition, researchers will be able to assess typical rock properties such as hardness, porosity, permeability, and structural strength.

Another exciting feature of the XDL is its modeling and simulation capabilities. The Modeling Lab will advance the science of rock mechanics, cutter design, and drilling fluids technology using computer-based mathematical models. Research will include the effect of fluids between the rock and the well bore during cutting and the role of geo-mechanics in estimating the potential for rock failure and stress caused by fluid flow in rocks.

A Bright Future for XDL
Much of the work done in the UDS will literally be cutting-edge research. Industry and the research community are anxiously awaiting the visualization results taken of the cutter at extreme condition. Even the rock debris generated from the experiments is expected to provide significant insight into the fundamental physics of the cutting process. As UDS experiments make an immediate impact in lowering the cost and risk of ultra-deep wells, the XDL’s rock star will become a legend in its own right, pumping up the volume of America’s oil and NG energy resources.