Method for Recovering Hydrocarbons from Subterranean Formations

Abstract

Recovery of viscous hydrocarbon from subterranean formations is assisted by using a plurality of novel U-tube type wells, each with dual wellheads, a moveable wellbore packer, a lateral section with a concentric communication zone and with sequential injection production perforations in which heat is injected into the proximal perforations and hot oil and produced fluids are produced from the distal perforations, the whole process being controlled by modulating the production flow where the wellbore fluids are controlled to act as a hydraulic seal to limit bypass of injected fluids. The injection-production displacement process moves axially along the wellbore in a sequential manner as hydrocarbon volumes are depleted by injected fluid displacement of oil and oil and water production.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority from provisional application 60 / 712,289 filed Aug. 30, 2005 and Disclosure Document 521,535 by Dr. Henry Crichlow.INTRODUCTION [0002] This invention relates generally to a new technology application and a new type of oil well for recovery of viscous hydrocarbons from subterranean oil bearing formations. The technology involves the novel use and application of equipment and techniques in which horizontal wells are drilled from the surface down to and across an oil bearing formation and back up to the surface, in a manner similar to that of drilling under a river crossing when laying pipelines across country. This new type of horizontal well is called a Uniwell™ because it has two surface wellheads one at each end of the axis of the horizontal system. Either wellhead can be used for either injection or production as needed by the operator. [0003] The technology is a new application using some elements of a...

AI Technical Summary

Benefits of technology

[0074] An object of this invention is to provide an improved method for recovery of oils from subterranean formations by exploiting the advantages provided by gravity drainage in the displacement process of heavy oils in porous formations using steam or combustion driven displacement processes. The use of a single modified well bore, with a downward, lateral and upward section, the uniwell™, has several engineering benefits including cost reduction, better fluid displacement and more engineering control of the injection and oil recovery process.

Problems solved by technology

This technology while theoretically possible is operationally difficult to hit such a small underground target, i.e the axial cross-section of a typical 8-inch wellbore using a horizontal penetrating drill bit.

This type of downhole flange connection is extremely difficult if not impossible to implement in current oilfield practice.

The laboratory demonstration in this patent shows that the annular steam zone is very conductive to oil production and allows premature steam breakthrough.

Based on this demonstrated observation, it is difficult if not impossible, to conceive a situation taught by this patent in which the injected steam as drive fluid will not preferentially flow under the hundreds of pounds injection pressure along the heated annular zone and thus bypassing the cold viscous oil saturated formation.

It is difficult to visualize the steam entering a cold highly viscous formation while a highly open wellbore is available for fluid flow away from the formation.

This situation is not only physically impossible but it thermodynamically impossible for the hot fluid to flow “against the pressure gradient”.

Very few of these prior art systems have been used in the industry with any success because of their technical complexity, operational difficulties, and being physically impossible to implement or being extremely uneconomical systems.

These include; the inability of the method to inject the hot fluid into a cold highly viscous oil in the formation; the inability to overcome the viscosity effect, wherein the viscosity of steam is less than 0.020 cp under the reservoir conditions which makes the flow of steam through porous media 5,000,000 times easier than cold high viscosity oil of 100,000 cp.

This flow ratio is based directly on the viscosity ratios of 100,000 / 0.02; the inability of the method or process to prevent bypass of injected fluid directly from the injector source towards the producing sink; the inability of the method or process to provide an effective seal to prevent high pressure injected steam from bypassing cold viscous oil impregnated formation and moving directly from the injector source towards the producing sink; the inability of the method or process to form a viable communication zone from the steam zone or chamber to the producing sink while preventing bypass and early breakthrough of steam; the inability of the process to utilize the significant gravity drainage effects created by the low density of the hot steam compared to condensed water and hot oil; the inability of the method to heat the formation effectively by physical contact between the steam and the rock formation such that the latent heat, which the major source of heat energy compared to the sensible heat, can be transferred to the rock and hydrocarbons efficiently; the requirement of long injection lead times of months to years of hot fluid injection, before there is any production response of the displaced oil; the use of overly complex equipment of questionable operational effectiveness to implement the method in the field.

Secondly, the large distance between the top of the formation and the bottom of the formation will cause condensation of the drive steam allowing essentially hot water to be produced at the bottom with low quality steam, both fluids being re-circulated back to the surface.

In addition the mechanism to heat the near wellbore can only be based on conductive heat transfer through the steel casing.

Since there is no formation rock contact with the steam fluid in which latent heat transfer to formation fluids and rock is the major heat transport system, the U.S. Pat. No. 3,994,341 method is incapable of delivering sufficient heat in a reasonable time to heat the formation sufficiently lower the viscosity of the oil, raise the porosity and permeability of the formation as taught in the present patent application.

To date, the majority of producing or injection horizontal well embodiments shown in the petroleum industry have but a single wellhead and are all limited by several physical and operational problems associated with the physical nature of the embodiments.

No effort to date has used this technology effectively for oil recovery in a manner and form such as the uniwell™ described herein.

This problem has continued to baffle the contemporary and prior art with possibly the only exception being the SAGD patent which uses two horizontal wells closely juxtaposed in a vertical plane.

Even this SAGD approach has inherent difficulties in initiating the hot oil flow between the two wellbores.

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