Method and downhole apparatus for matrix acidizing of a subterranean rock formation

#This application is a National Stage Entry of International Application No. PCT/US2022/036971, filed Jul. 13, 2022.

#The subject disclosure relates to matrix acidizing operations that enhance recovery of hydrocarbons from subterranean rock formations.

#The rate of hydrocarbon recovery from hydrocarbon-bearing subterranean rock formations (i.e., hydrocarbon reservoirs) is governed by the interplay of viscous and capillary forces that determine fluid transport in porous media, and several enhanced recovery techniques have been devised to increase the rate and completeness of fluid transport. One type of enhanced recovery technique is commonly referred to as matrix acidizing, which involves the supply or injection of fluidic chemical agents such as acids and other materials into the near-wellbore area of a hydrocarbon-bearing subterranean rock formation at pressures below formation fracture pressure to restore or enhance the permeability of the rock formation. The matrix acidizing is often carried out following damage to the near-wellbore area following drilling and fracturing operations. As the fluidic chemical agent (referred to herein as a “stimulating fluid”) contacts the rock formation at a treatment site or zone, formation rock (often carbonates) at or near the treatment site or zone can react to the stimulating fluid and undergo dissolution reactions that produce highly permeable channels or “wormholes” that enable fluid transport through the rock formation. Successful matrix acidizing is often characterized by the production of dominant wormholes that may have some degree of branching but extend into the rock formation and consume minimal amounts of stimulating fluid.

#The subject disclosure is further described in the detailed description below, in reference to the noted plurality of drawings by way of non-limiting examples of the subject disclosure, in which like reference numerals represent similar parts throughout the several views of the following drawings, and wherein:

#FIG. 1 is a schematic diagram of a wellsite with equipment provided for matrix acidizing a subterranean rock formation according to an embodiment of the present disclosure;

#FIG. 2 is a schematic diagram of an illustrative downhole tool for matrix acidizing a subterranean rock formation according to an embodiment of the present disclosure;

#The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the subject disclosure only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the subject disclosure. In this regard, no attempt is made to show structural details in more detail than is necessary for the fundamental understanding of the subject disclosure, the description taken with the drawings making apparent to those skilled in the art how the several forms of the subject disclosure may be embodied in practice. Furthermore, like reference numbers and designations in the various drawings indicate like elements.

#Matrix acidizing involves the injection or supply of stimulating fluid (e.g., hydrochloric acid) into the near-wellbore area of a hydrocarbon-bearing subterranean rock formation at a pressure below the formation fracturing pressure. As the stimulating fluid contacts the subterranean rock formation at a treatment site or zone, the formation rock (often carbonates) at or near the treatment site or zone can react to the stimulating fluid and undergo dissolution reactions that produce highly permeable channels or “wormholes” that extend radially (i.e., in a direction with a radial component orthogonal to the central axis of the wellbore) through the rock formation and enable fluid transport through the rock formation, which can restore or enhance the permeability of the rock formation.

#In embodiments, the process that forms such wormholes at a treatment site or zone can be logically partitioned into two time periods: an induction time period and a wormholing time period. The induction time period is the time from the first injection of the stimulating fluid to initiate one or more wormholes at the treatment site or zone. The wormholing time period is the time period that one or more wormholes propagate by further dissolution of the formation rock and extend radially into the rock formation. The volume of stimulating fluid injected during the induction time period can be greater than thirty percent of the total volume required for the matrix acidizing operations. Hence, minimizing the induction time period can significantly reduce the time and cost of matrix acidizing operations.