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The Steps We Take to Assure Well Integrity
Prior to drilling a well, Southwestern Energy evaluates the subsurface conditions in the area of the well to determine how such conditions may influence the design and construction of the well. This evaluation determines, among other things, the formations that contain underground drinking water resources, the proximity of the underground drinking water sources to the target injection zone and, the integrity of the confining layers above and below the target injection zone. We also evaluate the project area to identify abandoned wells and existing faults to assess their impact on the confining layers.
Prior to drilling a well, we design a casing and cementing plan that shows how the well will be constructed. At various stages of the drilling and completion process, we test the mechanical integrity of the casing and cement prior to moving on to the next stage. To prevent drinking water contamination and other pressure related problems, we use centralizers (which keep the casing centered in the well bore) at prescribed locations to ensure that cement is evenly distributed between the casing and the well bore and we monitor our pump pressures and fluid returns during the cementing process to ensure the adequate coverage of cement across the target injection zone, any hydrocarbon strata or any zone containing protected water. Properly cementing and casing a well and verifying its mechanical integrity prior to conducting hydraulic fracturing operations is critical to preventing gas migration. Casing pressure tests detect deficiencies before a well could create a potential safety or environmental problem.
Throughout the drilling and completion process, we have well control procedures in place to prevent gas leaks and well blowouts from occurring. Every well has specialized equipment, including a blowout preventer (BOP), which is a large valve at the top of a well that can be closed immediately if warranted by a change in pressure. We continually monitor pressure levels during the drilling process and we have an automatic alarm system that warns if the pressure becomes too high or too low. Our BOPs are regularly inspected, tested and refurbished.
Each stage of the hydraulic fracturing operation is closely monitored on a real time basis. Highly skilled personnel closely monitor pump pressures, fluid rates and annular pressures and take corrective action if abnormal pressure responses indicate a failure of mechanical integrity or fracture growth out of the target zone.
During the production phase, we closely monitor flow rate changes that are anomalous to the wells typical behavior and continue to monitor annular pressures for any changes. In addition, regular inspection of the wellhead assembly and equipment removed from a well during normal maintenance is inspected for leaks, corrosion or damage. If necessary, corrective action is taken to remediate any mechanical integrity issues throughout the wells life until the well is properly plugged and decommissioned. |
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