Matrix acidizing treatment

Matrix acidizing treatments are more often performed, nowadays, with sensors and data acquisition systems continuously recording the surface pressure and rate histories. According to a recently proposed methodology (15), these records can be used to compute downhole rate and pressure evolutions. The bottomhole pressure history is then compared to the theoretical response of an equivalent reservoir wherein a non-reactive fluid would have been injected according to an identical rate schedule. Following this method, the difference between both theoretical and actual pressure responses originates from the evolution of the skin of the true reservoir under the influence of the acid attack. Equation 1 is then used to derive the skin decrease from this pressure difference. 

Numerous matrix acidizing treatments of sandstone formations have been conducted since the mid-1960s. In addition to HCl and various HCl-HF mixtures, acetic and formic acids have been used, alone and in combination with HF. 

Matrix acidizing has application in both carbonate and sandstone formations. In sandstone formations, matrix acidizing treatments should be designed primarily to remove or dissolve add-removable damage or plugging in the perforations and in the formation pore network near the wellbore. 

In carbonate formations, matrix acidizing is principally a damage bypass treatment. If a carbonate formation is undamaged, a matrix acidizing treatment probably cannot be expected to do more than double the production rate. Carbonate matrix acidizing is discussed in part III of this book. 

I was once asked to design a matrix acidizing treatment for an exploratory well in the Middle East. The acid treatment was expected to be required in order to induce production and continue with the exploration program. The first question I asked was, What type of formation is it The answer was, Either a carbonate or a sandstone. I then contacted the service company representative assigned to this treatment to ask for more details. 

Prouvost, L., andM. J. Economides. 1987. Real-time evaluation of matrix acidizing treatments. Petroleum Science and Engineering. November. 

Behenna, F. R. 1995. Interpretation of matrix acidizing treatments using a continuously monitored skin factor. Paper SPE 30121, presented at the Society of Petroleum Engineers European Formation Damage Symposium, The Hague. 

B-3. Matrix acid treatment in a very high-temperature... 

B-8. Matrix acid treatment for a 500 ft section in a naturally fractured... 

The tables in this appendix present successful, nonroutine carbonate matrix acidizing treatment procedures. The examples are derived from published procedures used by other operators throughout the world. 

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