System for developing high pressure shale or tight rock formations using a profusion of open hole sinusoidal laterals

Abstract

A wellbore system to produce natural gas and / or oil from high pressure shale or tight rock formations using a profusion of open hole sinusoidal laterals to achieve comparable contact surface areas with multi-stage hydraulically fractured wellbores. The laterals are drilled in an orientation designed to intersect the dominant natural fracture system and are also drilled in a sinusoidal pattern to interconnect the individual rock facies within the targeted subterranean zone. The sequence of lateral drilling is toe to heel, with the open hole kickoff in the downward direction to facilitate easy re-entry upon drill string tripping. By drilling enough laterals to achieve comparable contact surface area with hydraulically fractured wells, the subject invention allows for comparable quantities of natural gas and / or oil to be produced from high pressure shale or tight rock formations at significantly lower capital cost.

Description

TECHNICAL FIELD OF THE INVENTION[0001]The present invention relates generally to the recovery of subterranean resources, and more particularly to a method and system for enabling commercial production of high pressure natural gas, condensate or oil from tight subterranean zones without the use of hydraulic fracturing.BACKGROUND OF THE INVENTION[0002]Subterranean deposits of shale or tight rock that contain high pressure natural gas or oil usually require hydraulic fracturing to create sufficient ‘contact surface area’ and flow paths to enable production of commercial quantities of hydrocarbons. While the hydraulic fracturing method of completing wells in high pressure shale or tight rock formations is commonplace in many subterranean deposits, it is very capital intensive and requires copious amounts of water and proppant.[0003]The ‘contact surface area’ of hydraulically fractured wells is calculated by multiplying the ‘frac height’ by ‘frac length’ by ‘number of frac stages’ comple...

AI Technical Summary

Benefits of technology

The present invention provides a method and system for producing natural gas, condensate and oil from subterranean resources through a profusion of medium length lateral well bores. This increases the total contact surface area between the rock and wellbores to enable commercial quantities of hydrocarbons to be produced. The method and system reduce the disadvantages and problems associated with previous systems, especially hydraulic fracturing, such as high costs. The invention also allows for the use of non-water based drilling and completions fluids, which maximizes the rock's capacity to flow gas and oil and reduces the size and complexity of the surface facilities. The individual lateral wellbores are structurally stable and remain open throughout the life of the well, thus, no restriction to flow occurs as it does in hydraulically fractured conduits that experience fracture closure and / or proppant embedment. The method of drilling sinusoidal horizontal laterals is easier to execute than adhering to a very narrow directional drilling window required by targeting a specific sediment bed within the larger shale or tight rock zone.

Problems solved by technology

While the hydraulic fracturing method of completing wells in high pressure shale or tight rock formations is commonplace in many subterranean deposits, it is very capital intensive and requires copious amounts of water and proppant.

The effective wellbore height is somewhat difficult to measure precisely because it needs to account for near wellbore effects, including drilling stress fractures.

The main problem in producing natural gas and / or oil from shale and tight rock is the extremely low permeability of the rock, which, until now, required hydraulic fracturing to create sufficient contact surface area for the hydrocarbons to flow from the surrounding rock into the wellbore where it flows, or is pumped, up to the surface facilities.

Without hydraulic fracturing the contact surface area between the rock and the wellbore is insufficient to flow commercial quantities of hydrocarbons.

Even very long horizontal wells, drilled within the shale or rock beds themselves, have insufficient contact surface area without the additional step of hydraulic fracturing.

However, after stimulating the well with 30 separate hydraulic fracture stages along this 9000′ long wellbore the well will produce approximately 500 barrels of oil per day over the first year.

Another problem in hydraulically fracturing shale or tight rock is that the water needed to fracture the rock causes a ‘reduced relative permeability’ effect in the rock matrix, and thus inhibits the flow rate of natural gas and oil.

Some operators have conducted hydraulic fracturing with non-water based systems, though these are even more expensive than the water based fracs.

Another problem with hydraulically fractured wells in shale or tight rock is the ‘reduced conduit flow capacity’ effect resulting from fracture closure and proppant embedment after the well has produced for a while and the overburden pressure causes proppant crushing and / or sediment deformation around the proppant.

Typical hydraulically fractured wells experience a steep decline in gas or oil flow rates, upwards of 80% loss in productivity, in just the first year.

This decline in production flow is the result of depletion of pore pressure in the rock surrounding the main wellbore and fracture conduits.

Fracture closure accelerates this decline due to the reduction of flow capacity in these conduits and thus reduces the effective contact surface area available to flow into the main wellbore and up to the surface.

Both these solutions drive up the cost of hydraulic fracturing.

Another challenge with wells in shale or tight rock is to drill the main wellbore in the precise sediment bed (within the larger shale or tight rock zone) that is best suited for the subsequent hydraulic fracturing step.

Thus, these wells must be drilled within a narrow directional window, which further drives up the cost of the well.

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