Patent Application: US-201514613717-A

Abstract:
a method of fracking carbonate - rich reservoirs , comprising injecting a cryogenic or chilled fluid followed by an acid into the reservoir , allowing the acid to etch the reservoir , and thereby increasing production of a fluid , such as water , oil or gas , from the reservoir . further , injecting a preflush into the reservoir and later injecting a postflush into the reservoir to displace the acid from the tubulars into the reservoir .

Description:
turning now to the detailed description of the preferred arrangement or arrangements of the present invention , it should be understood that the inventive features and concepts may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated . the scope of the invention is intended only to be limited by the scope of the claims that follow . the disclosure provides a novel method of improving the permeability of a carbonate - rich reservoir , the method generally comprising cryogenic acid fracturing , such that the cold temperature decreases the reactivity of the acid , allowing it to penetrate deeply into the reservoir before being spent . the major problems in obtaining fracture flow capacity in fracture acidizing are usually inadequate flow paths resulting from the etching process , and plugging of fracture channel with undissolved fines . etching flow channels in the fracture faces is usually feasible in heterogeneous carbonate rocks . however , in homogeneous rocks , the fracture faces tend to etch uniformly , resulting in fracture closure soon after completion of the acidizing job . dynamic laboratory etching tests are very useful in estimating the probability of a particular formation by fracture acidizing . in some formations , regular or high strength acid fracturing may not provide sustained production increases if large quantities of fines are released in the fracturing by the acid treatment , thus blocking the fracture . also , high strength acid may over - etch some very soluble carbonates , resulting in crushing of the pillars and posts after fracturing pressure is released or at a later date when reservoir pressure declines . thus , the fracture would close , blocking linear flow paths to the wellbore . the rubble formation created herein by the thermal stresses and frozen water in situ helps to solve the fines problem , providing a natural proppant and ensuring the fractures do not close after treatment . of course , not every limestone containing well is suited for acid fracking factors more favorable to acid fracturing treatment in carbonate include : the carbonate formation is predominately naturally fractured — which could lead to complications in case of proppant fracturing . the formation is heterogeneous with porosity and permeability streaks that are conducive to a higher degree , enabling differential acid - etching of the fracture walls . zone of interest is in close proximity to unwanted water or gas zone ( s ) not separated by stress barrier ( s ). formation permeability is relatively high and / or near wellbore formation damage exists . the well will not mechanically accept proppant . the present invention is exemplified with respect to ln2 and hcl . however , this is exemplary only , and the invention can be broadly applied to any acid and any cryogenic fluid that is cost effective and does not interfere with the carbonate reaction . the examples herein are intended to be illustrative only , and not unduly limit the scope of the appended claims . in closing , it should be noted that the discussion of any reference is not an admission that it is prior art to the present invention , especially any reference that may have a publication date after the priority date of this application . at the same time , each and every claim below is hereby incorporated into this detailed description or specification as a additional embodiments of the present invention . although the systems and processes described herein have been described in detail , it should be understood that various changes , substitutions , and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims . those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein . it is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims while the description , abstract and drawings are not to be used to limit the scope of the invention . the invention is specifically intended to be as broad as the claims below and their equivalents . all of the references cited herein are expressly incorporated by reference . the discussion of any reference is not an admission that it is prior art to the present invention , especially any reference that may have a publication data after the priority date of this application . incorporated references are listed again here for convenience : u . s . pat . no . 3 , 452 , 818 , gidley & amp ; 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