Conventionally, matrix acidising treatments have not been performed in HPHT wells with temperatures much above 150°C, because of the limitations on acid retardation technologies of hydrochloric acid (HCl) and the inhibition of corrosion of these fluids at elevated temperatures.

This paper presents the design and operational experience from a treatment performed on a gas well in a naturally-fractured, tight carbonate under conditions that were beyond the limit of conventional matrix acidizing experience. Stimulation of the well required acid to be placed below fracturing pressures into the natural fracture system beyond the near wellbore region. The reservoir was deep, sour and at high temperature and pressure.

Ensuring success of such an operation requires detailed design, involving extensive laboratory testing of fluid properties and design of placement techniques. Additional procedures and equipment are also required to effectively manage HSE risks and well integrity. This paper presents the critical factors in the design and operations planning stages, highlighting these with the case history for this well.

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