One of the main factors affecting the type of stimulation treatment in carbonates is reservoir properties. Acid fracturing effectiveness, in terms of economics and production increase, could be potentially more beneficial than matrix acidizing in case of low permeability of the stimulated reservoir due to creation of additional surface of fluid influx at the fracture faces. Matrix acidizing, on the other hand, makes more sense than hydraulic fracturing for the reservoirs where existing natural fractures and vugs have created conductivity similar to the expected conductivity of acid-etched hydraulic fractures.
However, if the reservoir has average permeability and is neither tight nor extremely fractured, it is a subject for additional studies on which type of treatment to choose. Mature and newly discovered oil fields within Triassic carbonates in Mangystau region, Kazakhstan, are examples of such reservoirs. The matrix acidizing and acid fracturing treatments have been actively exploited in the region, but no previous studies have been performed for Triassic carbonates in Mangystau regarding important questions about the comparative efficiency of the acid fracturing versus matrix acidizing treatments and the influence of reservoir parameters on expected treatment type and efficiency.
This paper considers post-stimulation production trends as a tool for evaluation of stimulation treatment effectiveness and suggests empirically derived conclusions for choosing the relevant stimulation strategy. The paper covers the analysis of 21 matrix acidizing and acid fracturing jobs performed in the Triassic carbonates of Mangystau region.