In matrix acid treatments, the goal is to stimulate the formation as deep as possible while distributing the acid uniformly over the total zone of interest. Uniform distribution is becoming even more important when intervals are long, horizontal, or when several zones with natural fractures predominantly take the reactive fluid.
In an oil-producing field in Europe, located in an environmentally sensitive area, an operator was challenged to efficiently place solvent and acid treatments by following a zero-spill philosophy. The environmental challenges were affronted by (1) developing novel solvent blends, eliminating mixing operations on location, (2) strict-fluid transfer procedures for solvents in closed-loop systems into specially constructed storage tanks, (3) blending acids by adding chemicals transferred with the help of the venturi effect, and (4) pumping and emulsifying the liquids using closed-loop systems, thus reducing the risk of spilling to the absolute minimum.
The difficulties in creating an oil external/acid internal emulsion was resolved by blending the hydrocarbon phase and acid phase separately in adopted containment and creating the emulsion fly just before the fluid is pumped down hole.
This paper describes the engineered process in finding a solution to the HSE challenges, beginning with laboratory testing to develop and optimize the solvent part and create the innovative acid system. Further, it will provide an overview of the equipment and techniques applied to overcome operational difficulties in reaching a spill-free operation in an operation where in a 12-month period, up to 5,000 m3 of solvent and 1,000 m3 of acid and emulsified acid is pumped. This paper will also explain the equipment specification and setup for creating the acid and emulsified acid systems ready for field application in an environmentally sensitive area.