In a novel chemical technology development, a robust liquid paraffin inhibitor is adsorbed onto an inert solid matrix. This solid fits within the size distribution range of a 20/40 proppant. As a manufactured product, the solid composite holds sufficient paraffin inhibitor to provide more than one year of continuous paraffin inhibition in the subject wells.
Five wells have been treated since November 2007 by including a solid paraffin inhibitor composite with the proppant during a hydraulic fracture. These include rod-pumped and electric submersible pump (ESP) wells. The wells produce oil, gas and water and oil production have ranged between 50 - 300 BOPD (barrels of oil per day). The traditional treatment approach for paraffin inhibition for similar wells includes continuous downhole chemical injection, batch treatment with a paraffin inhibitors or paraffin inhibitor squeezes. For paraffinic wells that still precipitate paraffin despite chemical treatment, it is common to remove accumulated paraffin by circulating hot water or hot oil in the well.
To be effective and economic, a solid inhibitor composite must have two critical characteristics. First, it cannot adversely affect the fracturing fluid or proppant pack, thus calling for extensive fluid compatibility, crush and conductivity testing. Secondly, it must perform to inhibit paraffin deposition for a period of time deemed to be cost-effective. Chemical effectiveness is measured in the lab through comparative pour point tests, cold finger deposition tests and through field observation history, e.g. the ESP's pulled for maintenance reasons show no sign of paraffin deposition unlike untreated offset wells. To date, except for a problem due to the loss of power in the field the operator reports paraffin deposition-free production.
Operator lifting cost is a function of lease expenses and oil production. When a well fails due to paraffin deposition the operator incurs a cost of remediation and a loss of production. By placing an inhibitor in the fracture, the paraffin is inhibited in the formation, at the perfs and in the tubulars. The cost of the inhibitor is more than justified by the savings in operational costs and the value of continuous and increased oil production.
In any market operators are driven by lifting cost (LC). Lifting cost is defined as the Lease Operating Expense (LOE) or Operating Expense (OpEx) divided by the BOED (barrels of oil equivalents per day). Simply put, the lower the LC the better the operation. In the case of a problematic paraffin instance the LC is affected by both increased LOE, e.g. hot oil or hot water expense to solubilize paraffin deposits, and decreased production represented by the NPT (non-productive time) that occurs during the hot oil/water. In a worst case, there may be a need for a workover in which case the OpEx and production figures are both affected in the wrong direction, i.e. increased OpEx and decreased production. This paper covers five wells for three different Permian Basin operators. Following is an overview of the wells treated and of the reasoning by which each operator made a decision to use the paraffin inhibitor composite as a means to impact the LC.
Operator 1: One well for this operator (A-44) was fractured with the paraffin inhibitor composite. The production engineers have reported no paraffin related problems to date (14 months). This field had used a variety of treatment regimens for paraffin control in the past. Currently the offset production is treated using periodic treater truck batch treatments. Hot water is used when these wells fail due to paraffin deposition. Due to the cost of remediation and the loss of production during down time the operator opted to try the composite material in a fracture.