Highly viscous fluids are used to initiate and propagate fractures and to place proppant in the fractures during the hydraulic stimulation process. These fluids can cause damage to the conductivity of the induced fractures if they are not properly cleaned out after the fracturing treatment. The clean-up process is aided by the degradation of the polymers, and in low temperature wells the breakdown of the polymer must be chemically induced. This paper win present data on a new fracturing fluid aimed specifically at stimulating low temperature and low pressure reservoirs. The system consists of a CO2 energized, cross-linked hydroxypropyl guar fluid. The gel is degraded by a traditional breaker that is activiated by a new, low temperature breaker activator. The fluid is effective in wells as cool as 60 °F and with BHP as low as 100 psi and should be particularly applicable to the shallow gas wells in the Alberta Medicine Hat and High level Keg River areas.


While the average U.S. well depth from 1975 to 1979 was increasing from 4541 ft. to 4925 ft. (an increase of 8%.)l, 2, the number of wells drilled increased from 41,477 to 50,332 (an increase of 21%)1,2. The result was an increase in the number of wells drilled with depths less than 5000 ft. It has been forecast that from 1980 to the year 2000 the average well depth will increase by 16% (from 5000 to 5814 ft) while the number of wells drilled will increase by 59%. (from 54,000 to 86,000). This again indicates that there will be an increase in drilling activity in wells that are less than 5000 ft. deep. The majority of this activity is and will be in fields that are already producing oil and gas. The wells in these fields have bottom hole temperatures of 125 °F or less, and many have low bottom hole static pressures (less than 500 psi).

The hydraulic stimulation of reservoirs under these conditions becomes somewhat more difficult due to the problems associated with the clean-up of the propped fractures. These problems arise from two sources:

  1. the difficulty in chemically breaking down the gel structure of the fracturing fluid after the fracturing treatment and,

  2. removing even properly broken gel from a packed fracture, the law pressure of the reservoir not affecting quick clean-up.

The objectives of this paper are to describe two techniques for fracture stimulation of low temperature and low pressure reservoirs. The first technique uses CO2-energized fluids and is designed for low temperature, low pressurized reservoirs. The second technique employs a nonenergized, more economical fluid that can be usedon low temperature wells that do not have low pressure problems.


The reasons for the existence of low pressurized reservoirs are numerous and varied. They include lack of permeability (e.g., the Morrow Gas Fields)3, decreasing or depleted reservoir potential, osmotic pressure differences (Alberta and San Juan Basin) 3, capillary pressure differences 3, dilation of pare volumes due to uplifting3 (Appalachian and Anadarko Basins) 3 and subsurface cooling due to overburden removal 3.

This content is only available via PDF.
You can access this article if you purchase or spend a download.