Abstract

A new method of completing multiple-layer formations has been successfully tested in the United States and Canada. This new method places sliding sleeve valves in the casing string and completes the well with normal cementing operations. The sliding sleeve valves are opened one at a time to fracture layers independently without perforating.

Completions using these casing valves are called Treat And Produce (TAP) Completions and have a unique design feature in the valves that allows a theoretically unlimited number of valves to be placed in a single well without incremental reductions to the internal diameter (ID). This near full bore feature allows normal cementing operations to be preformed with a special cement wiper plug. A control line is connected between sequential valves. When the bottom valve opens, the control line becomes pressurized and transfers the bore pressure to a piston in the valve immediately above. This piston squeezes a Cring and makes the ID smaller. At the end of the fracture treatment to the lower valve, a dart is dropped during the flushing operation. This dart lands on the squeezed C-ring and seals the bore inside the sliding sleeve. Pressure is then increased until the next valve is pumped open. When this valve opens, the next control line is pressurized, squeezing the next C-ring.

The main feasibility issue with this cemented sliding sleeve concept was fracture initiation pressure through the cement and into the formation without perforated holes. Significant laboratory testing was conducted which predicted fracture initiation pressure to be similar to that encountered in openhole or even lower. Fracture initiation pressures were closely monitored during several field installations and confirmed that perforations were not needed to initiate fractures in the formations.

This paper describes TAP Completions, how the TAP valves work, and how the valves performed. Information on a TAP

Completion with 6 layers is presented in detail and an overview of all installations to date.

Introduction

The US and Canada tight gas market is deploying new methods to efficiently stimulate multiple-layer reservoirs, but the most common method remains the same. Most wells are completed with cemented casing. To stimulate the reservoir, a plug is set, one or more layers are perforated and then the layer(s) are stimulated as a stage. This practice is repeated multiples times until all the layers are stimulated. Most wells are flowed within 24 hours to remove the treating fluids from the reservoir.

Operators seek to balance the quality and the cost of the stimulations vs. potential well production. One of the most important parameters affecting production is the number of layers fractured during a single stage. Stimulating multiple layers in a single stage is not ideal since layers with lower fracture gradients or formation pressure may take more of the treatment than planned, leaving the higher pressure layers only partially treated. This is becoming more of an issue as development wells are being drilled in more dense spacing, increasing the chances of treating some depleted layers.

The Treat And Produce (TAP) Completion system has been developed to allow the efficient treatment of individual layers in cemented casehole completions. TAP Completions use special casing valves that isolate individual layers one at a time without any interventions. The TAP valves are near full bore and do not require incremental reductions of ID and thus allow normal cementing operations. The TAP valves also have unique helical ports that align to any preferential fracture plane, regardless of the orientation of the valve in the casing string. These ports ensure a single bi-wing fracture plane is initiated from the well bore and the fracture initiation pressure is kept to a minimum.

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