Use of CT for well stimulation
Historically, the use of CT in fracturing became more prevalent with the inception of hydrajet fracturing technology. Before that, CT fracturing was limited to placement of small fractures in the formation and in some acidizing applications to bypass near-wellbore damage. Use of CT in fracturing stimulation is used to place large fractures by which the annulus now delivers primary fracturing fluid.
CT technology has evolved to produce fractures of more than 183-m (600-ft) half-lengths. In most formations, such fracture sizes would not be possible with fluid delivery originating from the CT alone, so the use of the annulus to deliver the primary fracturing fluid is a step change.
CT can be considered for many applications such as pipe cleaning, perforating, tool placement, logging, fishing, chemical placement, matrix treatment and drilling, among others. It is considered for so many applications because it can be rapidly deployed without the need for a drilling rig, it has the ability to fit through small restrictions like production tubing and it provides a seamless fluid conduit that has the rigidity for tool conveyance.
Inception of managed pressure fracturing
In response to the CT annular fracturing trend, whether fracturing a new well or refracking an existing well, Cameron has developed frack trees for CT applications, isolation tools to protect the CT from abrasive and corrosive frack fluids and equipment used to manage well-bore annular pressure while fracturing.
Having considered all elements of the operation and possible efficiencies, Cameron has developed the CT Annular Frac Tree featuring the FracGUARD Coiled Tubing Isolation Frac Head. This system supports the requirement to upsize the tree and components to accommodate larger fracture and proppant fluid volumes in a compact package. Also, the company offers pipe, manifold and personnel for managed pressure fracturing and wellbore flowback.
In CT operations there is additional pressure control equipment such as BOPs and lubricators along with the CT injector head that must be suspended above the well-head. Reduced height of the overall stackup improves the safety aspect of the operation. The company's vast selection of frack tree sizes allows operators to choose a solution so that there is enough annular space between the CT outer diameter (OD) and the inside diameter
(ID) of the frack tree.
FracGUARD is engineered to provide a flow area between the ID of the frack head and OD of the CT isolation sleeve. This enables high-volume flow rates ideal for "popping the toe." Because it is critical to protect the CT during the frack itself, FracGUARD functions as a barrier between the fluid entry ports of the frack head and OD of the CT. Such an isolation system allows the fracturing components to withstand today's high-volume fracture jobs while countering corrosive and erosive effects.
It has been documented that 40% of all fractures are not producing hydrocarbons. The use of CT annular fracturing, coupled with innovative systems, represents a step forward for operators choosing to use this technique to fracture or refrack their wells.