Increased Oil Recovery with Conductor Slot Recoveries
In a world starving for more hydrocarbons, one of the obvious solutions for maintaining or increasing production is to utilize existing infrastructure for recovering more reserves from both the original and adjacent fields. New drilling technologies are capable of reaching further than ever from the platform and the drilling efficiency is improving every day. The problem is however very often that all the well slots in the platform are occupied. Conductor Slot Recovery offers a simple and inexpensive way of drilling new wells from existing platforms by reusing well slots from nonproducing wells.
Building a new platform in today’s market is costly and time consuming. The advantage of using existing infrastructure is evident; why spend the money to build, install and hook up a new platform when you can drill one from an existing platform? When a platform well has ceased production, Conductor Slot Recoveries can offer a new start for an oil or gas field. Traditionally, downhole whipstocks and sidetracks have been the solutions to boost production; however this alternative can be costly and involve significant risk of failure. Also, in many cases downhole sidetrack will not be able to bring you to the target due to obstructions in the well, poor casing integrity or inadequate casing program in the old well.
The Conductor Slot Recovery operation offers a new and full casing program that gives the opportunity to reach pockets with full bore production potential from the pay zone. This offers a whole different flexibility for infield drilling. Combined with long reach drilling technologies this can contribute significantly to increased production from existing fields.
A typical Conductor Slot Recovery operation includes; permanent plugging and cementing of the old well to isolate all permeable zones, removing the old casing and conductor from seabed to surface, and finally the running and deflecting of the new conductor. The result is a freshly installed conductor that is ready for drilling of the surface casing. The Conductor Slot Recovery operation can be completed by a drilling rig or rigless with a jacking system. The rigless alternative can potentially save valuable rig days and reduce the overall cost of the new well significantly.
The Conductor Slot Recovery operation is a straightforward operation with few unknowns. However, it is nevertheless important that the engineering homework is being done properly. Issues that need to be covered during the planning phase are; study the seabed geometrics including anti-collision checks for the new conductor, check out structural capacity in conductor guides and bracing levels, decide whipstock placement – above or below the seabed, specify the right whipstock type, decide running method for the new conductor – drill or drive or combinations, etc. The optimal solution is normally dictated by the casing program, platform geometry and adjacent installations and their obstructions.
NCA has developed a range of unique and specialized abandonment techniques that are applied in its Conductor Slot Recovery operations. This includes the award winning IMCT – Internal Multistring Cutting Tool, for internal cutting of multistring conductors below the seabed – based on Abrasive Waterjet Cutting it creates a flat cut that is perfect for landing the conductor whipstock, unlike the mechanical cutting on drill pipe. For above seabed cutting NCA uses the subsea guillotine saw, either supported by divers or ROVs. To pull and lay out the multistring conductor, a specialized surface sectioning system has been developed which drills holes through the conductor and secures the inner casing strings before the multistring conductor sections are cold cut and laid out on deck. The combination of these special tools and its engineering and project management capabilities enables NCA to provide seamless turnkey Conductor Slot Recovery operations for any fixed platform.
Typical candidates for Conductor Slot Recovery are wellhead platforms installed in the 70’s and 80’s on water depths between 100 and 600 feet, an envelope that covers the majority of the older offshore fields in the mature oil and gas regions.