Producing Hydrocarbons from a Formation

Abstract

A system for and methods of producing hydrocarbons from a formation. A method may include drilling a wellbore in a formation, forming a first fracture in the formation that emanates from the wellbore, forming a second fracture in the formation that emanates from the wellbore and is approximately parallel to the first fracture, and simultaneously (a) injecting a fluid from an injection tubing string in communication with the second fracture and (b) producing hydrocarbons that travel from the first fracture into a production tubing string that is substantially parallel to the injection tubing string. The wellbore may be substantially horizontal. The fluid may increase pressure in an area of the formation adjacent to the first fracture.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional No. 61 / 780,010, and U.S. Provisional No. 61 / 779,998, both filed Mar. 13, 2013. These applications are incorporated by reference herein in their entirety.BACKGROUND[0002]1. Fields of Embodiments[0003]The disclosure relates generally to the field of producing hydrocarbons from a formation.[0004]2. Description of Related Art[0005]This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present disclosure. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.[0006]Substantial volumes of hydrocarbons exist in low-permeability and high-permeability formations around the world. Low-permeability formations may be formations that are near horizontal wells with multiple fracture stimulations distributed along the well and required to produce flu...

AI Technical Summary

Benefits of technology

The patent describes a method and system for producing hydrocarbons from a formation. The method involves drilling a wellbore in the formation, creating one or more fractures in the formation, and simultaneously injecting a fluid to increase pressure in the area adjacent to the fracture(s) while producing hydrocarbons from the fracture(s) into the wellbore. The system includes an injection tubing string and a production tubing string that are parallel to each other, with the second fracture being positioned to receive the fluid injected through the injection tubing string. The technical effects of the patent include improved wellbore placement, increased production of hydrocarbons, and more efficient use of wellbore space.

Problems solved by technology

The natural reservoir energy exploited in primary production such as oil and water expansion, evolution and expansion of gas initially dissolved in the oil, and rock compaction have limited ability to compensate for the volume of produced hydrocarbons and thereby to mitigate the pressure decline.

As the reservoir pressure declines because of production, so does the differential pressure between the reservoir and wellbore, resulting in declining production rates.

Primary production ends when the pressure is so low that the hydrocarbon production rate is no longer economical.

The lower the permeability of the formation the more difficult it is for pressure and fluid to be transmitted towards the well.

This results in lower initial rates, more rapid pressure decline, and lower recovery of hydrocarbons.

First, due to rapid pressure decline in the wellbore region, the production rate of recovered hydrocarbons typically declines quickly to less than 25% of the initial rate of recovery within a year.

Second, the total percentage of recovered hydrocarbons relative to the hydrocarbons contained in the formation is low.

The low formation permeability and resulting low rate of pressure diffusion through the reservoir, results in rapid pressure decline at the well and rapidly declining production rates of hydrocarbons.

Furthermore, since primary production processes rely on fluid expansion as their drive mechanisms they tend to have very low recovery levels in all oil reservoirs.

Disadvantages also result when operators use water-flooding or gas-flooding after using fracturing during primary production in a low-permeability formation.

However, they require the drilling and fracturing of additional injection wells or the conversion of existing production wells into injection wells.

Nonetheless, water-flooding in low-permeability formations is often limited by low injection rates due to the low-permeability formation, injection pressure constraints, plugging, separation between the wells and relative permeability effects.

A key limiting factor is that if the injection wells are placed in close proximity to the production wells, the fractures from the wells may intersect.

This results in high conductivity pathways between the wells that severely limit the rate of hydrocarbon production and the overall recovery that can be economically achieved.

Gas-flooding in low-permeability formations is often limited by poor sweep due to gravity override, viscous fingering and heterogeneity contrast.

These detrimental effects often cause fractures to intersect, thereby eliminating the pressure difference needed for sweep to occur.

These disadvantages are often exacerbated in low-permeability formations because of tight well spacing and higher permeability streaks.

Additional disadvantages may also result when the aforementioned drive mechanisms are used in low-permeability or high-permeability formations.

The effectiveness of water injection for improved recovery is sometimes adversely affected by reduced injectivity due to plugging of injection wells with solids, scale, oil, etc.

Enhanced recovery techniques, such as injection of miscible gases, surfactants, solvents, polymers, modified brines, or steam can sometimes be applied to high permeability reservoirs to improve recovery, but the use of these techniques is often uneconomic.

There is a significant time difference between when these relatively expensive fluids are injected into an injection well when that incremental hydrocarbon production occurs at a producing well.

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