In the oil industry, different methods are used to increase production of an oil or gas well. The most common involve pumping various chemical into the well usually at a high pump rates and pressures. This process is call Stimulation. One such method is referred to as Hydraulic Fracturing.

Hydraulic Fracturing involves pressuring against the producing formation with a fluid until the formation actually splits or fractures. The fluid, which is usually of a special chemical formulation, will carry sand at various concentrations. This sand/fluid mixture is pumped into the fracture usually at high pump rates. When the pump pressure against the formation is stopped, the fracture will begin to close due to the weight of the earth(overburden) pushing down on the fracture. The purpose of filling the fracture with sand is to hold the fracture open when the stimulation process is completed. The fracture filled with sand, then provides a very permeable flow path for oil or gas to flow from the fracture face, into the fracture and then into the well bore.

During pumping, the fracture will continue to grow outward from the well until the fluid leaking out of the fracture is equal to the amount of fluid being pumped into the fracture. At this point, the fracture will accept no more sand. The sand then backs up into the well bore and completely shuts off entry out of the well bore. This is referred to as a Alock-up@.When this happens while pumping, the pressure immediately starts to rise and the pumps must be stopped before the pressure reaches a point that equipment and pipe will burst.

Many times the operators of the pumps cannot react in time to prevent the pressure from rising above the rupture pressure. To relieve the pressure when it reaches a certain value, a devise commonly called a Pop-off Valve is put into the pump line. It is set to open at a predetermined pressure and divert the flow out into the open atmosphere.

Existing Pop-Off Valves have the following shortcomings:

Unreliable pop off pressure settings.

When activated, sand is trapped under the valve, which prevents it from resealing.

Limited flow rates through the valve.

Difficult to redress and maintain under field conditions.

LaFleur Petroleum Services has invented such a device that addresses these shortcomings. Refer to the attached drawings Figs. 1 & 2.

The primary components are the Piston (1) and the LAFLEUR PETROLEUM SERVICES= patented LPS Packoff (2). Notice that the Piston (1) has a larger top base area than its bottom base area. The bottom base area is exposed to the pressure that is in the high-pressure pump line by way of the Pump Line Cap (4) entry. The Top Base Area is exposed to a preset Nitrogen pressure.

The LPS Packoff (2) is located in the Main Body (7). The small diameter part of the Piston (1) is inserted through the LPS Packoff (2) . The Piston Ports (6) are then located inside and below the LPS Packoff (2) when the unit is in the Aclosed@ position.

When the unit is assembled, the Nitrogen Chamber (8) is charged with nitrogen to a pre-selected pressure. This pre-selected pressure will create a force on the large base area of the Piston (1). When the pump pressure on the bottom base area of the Piston (1) reaches a valve in which the pump pressure force created on the bottom base area exceeds the nitrogen force on the top base area, then the Piston (1) will start to move up. As the pressure continues to increase, the Piston (1) will continue to compress the Nitrogen and move further up until the Piston Ports (6) move out of the LPS Packoff (2) and expose the Piston Ports(6) to the internal chamber of the Main Body (7). Fluid will then flow from the Pump Line, into the Piston (1), out the Piston Ports (6) and into the atmosphere.

This will then keep the pump pressure from further increasing and give the time needed for the operators to stop the pumps. When the pump pressure then drops so that the force from the Nitrogen pressure is greater the force exerted on the bottom area of the Piston (1), then the Piston (1) will move downward until the Piston Ports (6) are again under the LPS Packoff (2). This will then seal the pressure in the pump line. It is now ready to function again by popping off should the pressure in the pump line rise to create a force that is greater than the preset nitrogen pressure force.

Most pop off valves in use in the field utilizes a cone shaped plunger to seal against an elastomer seat. When the plunger is activated, it moves away from the seat. When the plunger moves back against the seat to try to seal, sand from the fracturing fluid is trapped between the plunger and its seat. Thus, a seal cannot be achieved.

When the Piston ports (6) move through the LPS Packoff (2) to return to their original position, the LPS Packoff (2), which fits tightly around the Piston (1), wipes the Piston (1) clean of sand as the Piston (1) and ports move though the LPS Packoff (2). Thus the LPS Packoff (2) is sealing against a clean and sand free area of the Piston (1).

For setting the pressure at which the Piston Ports (6) will have traveled above the LPS Packoff (2), a chart is furnished that illustrates how much pressure should be applied to the Nitrogen Chamber (8) in order for the Piston Ports (6) to travel above the LPS Packoff (2) when the pump pressure reaches the desired valve. For example, for the valve to relieve the pump pressure when it reaches 7500 psi, the NITROGEN CHAMBER (8) should be charged to 600 psi.

NOTABLE FEATURES:

1. When sand laden fluid is diverted though the Piston Ports (6) and into the atmosphere, the o=ring seal (9) prevents the sand from going below the seal and being trapped between the Piston (1) and the Main Body (7). If this were to occur, then the Piston (1) could not travel to its fully stroke position. The sand would stop it.

2. The LPS Packoff (2) is easily and quickly changeable on the well site. The Pump line cap is removed which exposes the LPS Packoff (2). The LPS Packoff (2) is a one-unit seat that fits into a slot in the Main Body (7). This insert is pulled out of the slot with simple tools and a new insert put in place. The Pump Line Cap (4) is then screwed back onto the Main body (7).