By: Adam Larson, Staff Writer, Shale Media Group
As 2015 is winding down, operators in eastern Ohio’s Utica Shale are still drilling away. At this point in time, when it comes to drilling, they are following a straightforward recipe.
Selecting a well location takes an army of geologists and reservoir engineers – not to mention a swarm of landmen and women to pin down large plots of acreage. Acquiring the land is the hard part. Drilling the wells comes easier.
Nestled in the Ohio country, both the lease road and pad are carved out by third party excavation crews. In fact, the entire job site is bustling with third party companies that are specialized in a niche element of the drilling process.
Two-thirds of the pad is covered with containment. The cellar is dug with an 8-10 foot diameter, which allows for the production tree to be accessible at surface. Along with the cellar, the conductor pipe is installed, ranging with a fairly small diameter of 20 inches. The pipe is nudged down 50-100 feet deep, provides initial wellbore stabilization, and is essentially used to rig up on when drilling rig is mobilized.
All in all, if you were to look at an aerial snapshot of the pad, there’s an orchestrated symphony of equipment. Trailers, the actual rig, drill pipe, mud pumps, gas busters, shale shakers, centrifuges, air compressors, and generators scatter the pad. Depending on the operator and job site, different sized rigs are used, which all leverage technology in some fashion, as the driller sits in the rig’s doghouse, observing 4-5 monitors, the screens filled with pressures, rate of penetrations (ROP), torque, weight on bit, and pump stroke length.
Some of the rigs actually “walk” from well to well. Modern shale gas resources allow for the implementation of horizontal drilling, creating a pad with as many as eight wells. With this in mind, newer rig technology can be a useful tool in driving efficiencies in a tight commodity price environment, as the rig can “walk” within less than 30 minutes.
Simplifying things, when drilling a well, the hole diameter starts wide at the surface and ends narrow at the well’s toe. Drilling takes place in intervals: the conductor, surface, intermediate, and production phases. Boiling the process down, third party companies will drill, place casing, pump down cement, and repeat until desired depth is reached.
Vertically, the surface phase is placed with 13, 3/8” diameter casing at about 500 – 600 feet. The intermediate phase employs 9, 5/8” diameter casing at about 1,800 – 2,500 feet. And, the production phase typically uses 5, ½” diameter casing at about 6,500 – 7,500 feet and continues into the horizontal all the way to the toe.
While meeting this desired footage vertically, the kickoff point (KOP) is reached and the drill bit starts to slowly build the curve of the well. An entirely different third party contractor’s sole job is to build the curve, land the curve, and drill the lateral.
It takes about 15-24 hours to drill and land the curve at a slow ROP of 80-100 feet/hour. When transitioning into the lateral, an average of 300-400 feet/hour is typical, as total time varies with measured depth (MD) of the well. The MD of a well can range anywhere between 14-17,000 feet, as operators continually extend their laterals as it becomes more cost efficient. Likewise to the beginning of the KOP, the entire lateral is wrapped with production casing.
In the modern shale gas age, directional drilling is nailed to a science. Conventional directional drilling, also known as slide drilling, is done by drilling with a mud motor rotating the bit downhole without rotating the drillstring from the surface.
However, a growing number of operators are taking advantage of a hotter piece of directional drilling technology called a rotary steerable system (RSS). RSS utilizes specialized downhole equipment, which replace mud motors. Altogether, RSS can be used to drill directionally with continuous rotation from the surface, eliminating the “sliding” of a mud motor.
Lastly, one of the most critical parts of the drilling process is the mud and drilling fluids circulation system. Mud is pushed down the borehole for the entire drilling process and is used to cool the drill bit while pushing cuttings up the annulus and to surface.
Most of the Utica, depending on the operator, uses synthetic oil based mud (SOBM) that is more biodegradable and environmentally friendly opposed to other types of mud. For the production string, approximately 73-75 barrels of drilling fluid is needed. The sheer volume of drilling fluid needed throughout drilling a well is typically the most expensive component compared to other drilling equipment and processes on-site.
Circulating components include a mud pump, suction line, mud pit, shale shakers, return line, rotary hose, and swivel. Usually the makeup of the fluid includes weighing additives like barite to allow balanced drilling at increased depths, emulsifiers to disperse insoluble liquids, shale inhibitors to prevent shale swelling, and wetting agents to help move cuttings across the shale shaker. The third party contractor’s mud engineer collects and analyzes mud and cutting samples to get the correct weight and chemistry of what’s going downhole.
It takes about 12-15 days to drill a well. After the crew rigs down and moves out (RDMO), the pad is handed off to the completions and hydraulic fracturing crew. With improved efficiencies and technologies, the shale world is constantly changing.
*This article is the first in a series of articles looking at the entire upstream process. Future editions of the ONG Marketplace will include articles on completions, construction and facilities, and production in the Upstream section.
Shale Media Group (SMG) is the news, information, and education resource dedicated to the shale oil and gas industries by messaging across video, Internet, publications, events, and radio. For more, check out ShaleMediaGroup.com to access all platforms. Adam Larson is a Staff Writer with Shale Media Group. He also studies Petroleum and Natural Gas Engineering at Penn State University. Contact him at .