HYDRAULIC FRACTURING and Chemicals Management
Advancements in horizontal drilling combined with hydraulic fracturing have allowed for the development of previously marginal and uneconomic gas and oil-bearing geologic zones.
Hydraulic fracturing has become a key element of oil and natural gas development within the United States. Today, it is part of the process of drilling and completing most onshore oil and natural gas wells. This well-stimulation method is a process that has been used since the 1940’s to coax oil and gas out of tight shale formations more than a mile underground. Currently, more than 90% of all crude oil and natural gas wells drilled in the U.S. employ hydraulic fracturing. Although the injection process for each well typically lasts only two to three days, the well may produce for 20 years or more.
Commonly known as “fracking,” the stimulation process involves injecting a mixture of water, sand and a small amount of chemical additives at high pressure into rock formations many thousands of feet below the surface of the earth.
After a preliminary hole is drilled to below the lowest aquifer, large diameter surface casing is run into the hole, below the aquifer and cemented to the surface. A blowout preventer is installed to protect the rig from high pressure geologic zones. A smaller drill bit is then used to drill from the base of the surface casing to the kick off point, at which point the wellbore is drilled at an angle (8-10 degrees per 100 feet) to gradually transition from vertical to horizontal. A smaller casing string is set in the hole and cemented in place. The multiple layers of cement and casing in the well prevent communication and contamination between the well and the aquifer. At this point, the horizontal drilling of the wellbore can be completed, and a production liner can be set in the horizontal section of the well. The drilling rig is moved off location after all wells have been drilled on the pad, making room for completion equipment.
With completion equipment in place, a perforating gun is sent downhole and used to create small holes in the production casing. A mixture of water, sand, and small quantities of chemical are then pumped down the well under high pressure. The mixture flows into the fractures and then the water is pumped back out leaving the sand in place, holding the fractures open, and allowing the oil and gas to flow out of the rock and up the wellbore to the surface. Hydraulic fracturing for each well is generally done in stages to help control the location of the fractures and the flow of the mixture into the rock.
The ingredients used in fracking fluids vary according to geology. Whiting designs each of its hydraulic fracturing jobs and fluid used to the specific characteristics of the rock we are operating in. In general terms, water makes up more than 90 percent of the solution. Sand, or proppant, constitutes approximately 9 percent and additives make up less than 1 percent of the total volume. The relatively small amount of additives generally consists of items you can find under your kitchen sink, as you can see here.
After all stages are completed, the wellbore can be cleaned out and turned on to produce oil and gas. Whiting designs each completion job to maximize the performance of the well.
Whiting manages the risks associated with hydraulic fracturing in several ways. During the fracturing process, neighboring wells are often shut-in, or “frac protected”, to prevent damage that can occur through communication between the wellbores. As described in the drilling and completion process, multiple layers of cement and casing protect the ground around the wellbore, including any aquifers. Specialty pressure control equipment is used to protect surface equipment from high surface treating pressure. Cement and casing evaluation logs are run to insure the proper amount of cement is in place to secure the production casing and evaluate the integrity of the production casing. Frac strings are generally used as an additional layer of protection for the production casing during fracturing and other completion processes. In 2017, Whiting did not experience any well integrity failures associated with hydraulic fracturing processes.
Whiting believes trust and transparency is essential to the continued progress of energy development. In furtherance of this belief, Whiting is dedicated to disclosing the chemicals used in our completion fluids. We provide a Hydraulic Fracturing Fluid Product Component Information Disclosure Report for each of our wells. Nearly 1,900 of these reports may be found on the FracFocus website. In addition to the operator and the fluid content, each report identifies the API number, job start and end dates, state, county and well name. Whiting also works with all its vendors to report fluids used in hydraulic fracturing to FracFocus.
To identify, evaluate and address matters related to induced seismicity, Whiting has created an Induced Seismicity Committee, that is focused on identifying and mitigating induced seismicity risk and liability pertaining to produced water disposal and hydraulic fracturing.