Method and apparatus for producing unconventional oil at shallow depths

Abstract

An oil production well is drilled into a kerogenous chalk source rock comprising (i) type IIs kerogen and (ii) shallow naturally-occurring unconventional oil derived from the type IIs kerogen that is resident within pore space of the source rock. In some embodiments, the production well is drilled at a location where the geothermal gradient is at least 3 degrees C. per 100 m is present at or near the production well. It is believed that the presence of this geothermal gradient accelerated maturation of the type IIs kerogen of the source rock to convert a portion of the type IIs kerogen into the unconventional oil. In some embodiments, the shallow production well is non-vertical. In some embodiments, at depths that are shallow and within the source rock, the production well is cased and perforated. Oil from the source rock may be produced via the production well and the shallow-depth perforated locations thereof.

Description

BACKGROUND AND RELATED ART[0001]In the last few years, the oil industry in the United States has developed methods for producing unconventional gas and oil from very low permeability source rocks. In these unconventional gas and oil plays, the gas and oil is still contained within the original source rock and has not migrated to a reservoir and trap.[0002]For example, the Bakken shale in North Dakota has been extensively produced using long horizontal wells which are stimulated with multiple propped hydraulic fractures. These Bakken wells are typically at depths greater than about 3000 m in order for the Type I kerogen to have matured over geological time sufficiently to generate oil and gas. Even though the Bakken oil produced is low viscosity and rich in NGL (natural gas liquids), because of the depth of the wells and the many stages of hydraulic stimulation that are required, these unconventional wells are very expensive and only a very small percentage of the unconventional oil ...

AI Technical Summary

Benefits of technology

[0003]Instead of relying on artificial heat to pyrolyze kerogen of a kerogenous chalk into pyrolysis fluids (i.e. as is common in in-situ conversion processes (ICP)), it is possible to drill for oil in a kerogenous chalk where natural events (e.g. historical volcanic or other geothermal activities) supplied sufficient thermal energy to convert ker...

Problems solved by technology

Even though the Bakken oil produced is low viscosity and rich in NGL (natural gas liquids), because of the depth of the wells and the many stages of hydraulic stim...

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