Throughout the history of the oil and gas industry, well control has been a fundamental and significant concern not only because it is a safety issue but also a health and environmental one as well. As the industry has drilled deeper wells in different environments, the more critical well control issues have become. An operator for an inland water well in southern Louisiana considered all this history when solid expandable tubular technology was chosen to maintain well control.
This paper describes the concerns and the steps taken for well control while running solid expandable tubular products in two wells, one located in inland waters and one deepwater. The paper cites concerns about overcoming well control issues while making-up, running, and expanding solid expandable tubular liners and the solutions and steps taken in a well control situation during the deployment of the solid expandable tubular openhole liner.
Well control has been a problem for operators since the first oil wells were drilled in the mid-nineteenth century. If a well is not controlled properly, blowouts can occur. Blowouts not only squander oil and gas but they can also injure or kill crewmen.
To control a well while drilling requires constant monitoring of mud circulated down the drillstring and back up the annulus between the drilled hole and the drillpipe. The hydrostatic pressure of the mud at the bottom of the hole must be greater than the formation pressure to prevent formation fluids from entering the wellbore. Should mud weight become less than formation pressure, then well flow may occur. If this happens, the mud weight will have to be increased to prevent uncontrolled well flow from the formation.
The same situation occurs while running an expandable liner because, as with drilling, the well flow must be contained. Solid expandable tubular technology was developed originally to meet the challenges facing the oil industry posed by drilling in high pressure zones, deepwater environments, and troublesome sub-salt plays. Earlier in the development of solid expandable tubular technology, a certain prejudice existed against solid expandable tubulars regarding well control. While traditional technologies were well established to control a well, it was seen by many in the oil and gas industry that expandable tubulars were untested and had too many problems controlling a well. The constraints are somewhat different, however, while running an expandable liner.
The liner shoe creates surge pressure as it is run in the hole because of the right clearance between the bottom of the liner (shoe) and the base casing. These surge fluids have a tendency to flow into the formation. Surge pressure is dependent on several factors including the speed the liner is run, the outside diameter (OD) of the shoe in reference to the diameter of the base casing and the open hole, the mud weight, and the mud viscosity. There are two methods to run expandable liner in the hole: with the float valve in the closed (enabled) position and with the float valve in the open (disabled) position.