Beyond the Frac: Using the Fracture Process as the Delivery System for Production Chemicals Designed to Perform for Prolonged Periods of Time

Abstract

Abstract It is a well-accepted practice to add production chemicals to a formation through a squeeze process. These are designed to place chemical in the near well area and treat the fluid for scale, paraffin, salt, etc. Now, frac-fluid approved chemicals are added to the fracture in order to place products deeper in the formation. In addition, concentrated solid versions of some chemicals have been formulated to provide prolonged treatment. This paper deals with the application of three production chemicals through the fracture fluid process. These chemicals were used to address the problems of scale deposition, bacteria-related corrosion and oxygen induced corrosion. Fracture fluids are complex blends of chemicals designed to perform specific purposes in a specific order during the fracturing process. The addition of non-frac chemicals adds another level of complexity to the formulation and compatibility processes. Thus, it was necessary to limit the scope of production chemical choices and to seek out the most robust products. To date the following types of production chemicals have been added to a variety of fracture fluids: scale inhibitors, salt inhibitors, oxygen scavengers, biocides, asphaltene dispersants and relative permeability modifiers. Gas hydrate inhibitors and paraffin inhibitors, although not yet applied, have been tested and approved for compatibility. In the future the authors hope to report on the outcome of fracturing and chemical programs that addressed the problems that required the use of these chemistries. The significance of this new area of chemical application falls into two levels. For a land or shallow water well where intervention costs are a major issue then the choice to add production chemicals to the fracture depends on the severity of expected treatment problems, the remoteness of the well and other operational and economic drivers. However, in the case of a deep-water well the application of key production chemicals applied during the initial stimulation could make the difference between a highly profitable well and a well that sees a production decline and requires an expensive intervention. Introduction The production of oil and gas is a continuous process for the life of the well. What is done during an early stage can affect, positively or negatively, the quality of the produced product as well as the assets associated with the production. This paper discusses the relationship between the fracturing process and the chemical inhibition process. In particular it looks at a case where three production chemicals (scale inhibitor, biocide and oxygen scavenger) were added to fracture treatments. A well is fractured for a specific purpose. That purpose does not always complement the resulting effort to prevent and inhibit problems associated with the subsequent production. In fact, the fracturing process can inadvertently contribute to production problems. In order to optimize the fracturing process and the chemical inhibition a program was established in which the fracture and chemical technologists designed programs by which the chemical could be added to the fracture fluid with minimal impact on the fluid itself. This was done to take advantage of several opportunities provided by the fracture. These include:Deeper placement of chemical into reservoirPlacement of chemical ahead of the problem areaInitiation of inhibitor process in the fracture fluidCurtailing of certain corrosion, scale and bacterial processed early in the production processReduce and/or delay the need for intervention and increase to cost of operation Szymczak, et al1 and Webb, et al2 have reported on the addition of a scale inhibitor in the fracture process. In both cases the scale inhibitor had been adsorbed onto a solid matrix and added to the proppant. Both report positive scale inhibition results. In the case of the present paper the scale inhibitor was added as a liquid in the frac fluid on-site.