1. Field of the Invention
The present invention relates to systems and methods for producing or delivering heat at or near the down hole end of production tubing of a producing oil or gas well for improving production therefrom.
2. Background Information
Free-flowing oil is increasingly difficult to find, even in oil wells that once had very good flow. In some cases, good flowing wells simply xe2x80x9cclog upxe2x80x9d with paraffin. In other cases, the oil itself in a given formation is of a viscosity that it simply will not flow (or will flow very slowly) under naturally ambient temperatures.
Because the viscosity of oil and paraffin have an inverse relationship to their temperatures, the solution to non-flowing or slow flowing oil wells would seem fairly straight forwardxe2x80x94somehow heat the oil and/or paraffin. However, effectively achieving this objective has proven elusive for many years.
In the context of gas wells, another phenomenaxe2x80x94the buildup of iron oxides and other residues that can obstruct the free flow of gas through the perforations, through the tubing, or bothxe2x80x94creates a need for effective down hole heating.
Down hole heating systems or components for oil and gas wells are known (hereafter, for the sake of brevity, most wells will simply be referred to as xe2x80x9coil wellsxe2x80x9d with the understanding that certain applications will apply equally well to gas wells). In addition, certain treatments (including xe2x80x9chot oil treatmentsxe2x80x9d) for unclogging no-flow or slow-flow oil wells have long been in use. For a variety of reasons, the existing technologies are very much lacking in efficacy and/or long-term reliability.
The present invention addresses two primary shortcomings that the inventor has found in conventional approaches to heating oil and paraffin down hole: (1) the heat is not properly focused where it needs to be; and (2) existing down hole heaters fail for lack of design elements which would protect electrical components from chemical or physical attack while in position.
The present inventor has discovered that existing down hole heaters inevitably fail because their designers do not take into consideration the intense pressures to which the units will be exposed when installed. Such pressure will force liquids (including highly conductive salt water) past the casings of conventional heating units and cause electrical shorts and corrosion. Designers with whom the present inventor has discussed heater failures have uniformly failed to recognize the root cause of the problemxe2x80x94lack of adequate protection for the heating elements and their electrical connections. The down hole heating unit of the present invention addresses this shortcoming of conventional heating units.
Research into the present design also reveals that designers of existing heaters and installations have overlooked crucial features of any effective down hole heater system: (1) it must focus heat in such a way that the production zone of the formation itself is heated; and (2) heat (and with it, effectiveness) must not be lost for failure to insulate heating elements from up hole components which will xe2x80x9cdrawxe2x80x9d heat away from the crucial zones by conduction.
However subtle the distinctions between the present design and those of the prior art might at first appear, actual field applications of the present down hole heating system have yielded oil well flow rate increases which are multiples of those realized through use of presently available down hole heating systems. The monetary motivations for solving slow-flow or no-flow oil well conditions are such that, if modifying existing heating units to achieve the present design were obvious, producers would not have spent millions of dollars on ineffective down hole treatments and heating systems (which they have done), nor lost millions of dollars in production for lack of the solutions to long-felt problems that the present invention provides (which they have also done).
It is an object of the present invention to provide an improved down hole heating system for use in conditioning oil and gas wells for increased flow, when such flow is impeded because of viscosity and/or paraffin blockage conditions.
It is another object of the present invention to provide an improved design for down hole heating systems which has the effect of more effectively focusing heat where it is most efficacious in improving oil or gas flow in circumstances when such flow is impeded because of oil viscosity and/or paraffin blockage conditions.
It is another object of the present invention to provide an improved design for down hole heating systems for oil and gas wells which design renders the heating unit useful for extended periods of time without interruption for costly repairs because of damage or electrical shorting caused by unit invasion by down hole fluids.
It is another object of the present invention to provide an improved method for down hole heating of oil and gas wells for increasing flow, when such flow is impeded because of viscosity and/or paraffin blockage conditions.
In satisfaction of these and related objects, the present invention provides a down hole heating system for use with oil and gas wells which exhibit less than optimally achievable flow rates because of high oil viscosity and/or blockage by paraffin (or similar meltable petroleum byproducts). The system of the present invention, and the method of use thereof, provides two primary benefits: (1) the involved heating unit is designed to overcome an unrecognized problem which leads to frequent failure of prior art heating unitsxe2x80x94unit invasion by down hole heating units with resulting physical damage and/or electrical shortages; and (2) the system is designed to focus and contain heat in the production zone to promote flow to, and not just within, the production tubing.