## CATIONIC VISCOELASTIC SURFACTANT WITH NON-CATIONIC CORROSION 

## INHIBITOR AND ORGANIC ANION FOR ACIDIZING 

[0001] The inventions are in the field of producing crude oil or natural gas from subterranean formations. More specifi› cally, the inventions relate to increasing the viscosity of a well fluid for acidizing a subterranean formation, for example, matrix or fracture acidizing of carbonate formations, leak-off control in acid fracturing, and diversion in matrix acidizing. 

## Oil & Gas Wells 

[0002] To produce oil or gas from a reservoir, a well is drilled into a subterranean formation, which may be the res› ervoir or adjacent to the reservoir. Typically, a well bore of a well must be drilled hundreds or thousands of feet into the earth to reach a hydrocarbon-bearing formation. 

[0003] It is desirable to extend the production of wells and to avoid early abandonment when productivity decreases as a result of low natural permeability or formation damage. 

## Well Servicing and Well Fluids 

[0004] Well services can include various types of treat› ments that are commonly performed in a wellbore or subter› ranean formation. For example, stimulation is a type of treat› ment performed to enhance or restore the productivity of oil or gas from a well. Even small improvements in fluid flow can yield dramatic production results. 

[0005] Stimulation treatments fall into two main groups: hydraulic fracturing and matrix treatments. Fracturing treat› ments are performed above the fracture pressure of the sub› terranean formation to create or extend a highly permeable flow path between the formation and the well bore. Fracturing treatments are often applied in treatment zones having poor natural permeability. Matrix treatments are performed below the fracture pressure of the formation. Matrix treatments are often applied in treatment zones having good natural perme› ability to counteract damage in the near-wellbore area. 

## Hydraulic Fracturing 

[0006] The purpose of a hydraulic fracturing treatment is to provide an improved flow path for oil or gas to flow from the hydrocarbon-bearing formation to the well bore. In addition, a fracturing treatment can facilitate the flow of injected treat› ment fluids from the well into the formation. A treatment fluid adapted for this purpose is sometimes referred to as a fractur› ing fluid. The fracturing fluid is pumped at a sufficiently high flow rate and pressure into the wellbore and into the subter› ranean formation to create or enhance one or more fractures in the subterranean formation. Creating a fracture means mak› ing a new fracture in the formation. Enhancing a fracture means enlarging a pre-existing fracture in the formation. 

[0007] A newly-created or newly-extended fracture will tend to close together after the pumping of the fracturing fluid is stopped. To prevent the fracture from closing, a material is usually placed in the fracture to keep the fracture propped open and to provide higher fluid conductivity than the matrix of the formation. A material used for this purpose is referred to as a proppant. 

## TECHNICAL FIELD 

## BACKGROUND 

[0008] A proppant is in the form of a solid particulate, which can be suspended in the fracturing fluid, carried down› hole, and deposited in the fracture to form a proppant pack. The proppant pack props the fracture in an open condition while allowing fluid flow through the permeability of the pack. The proppant pack in the fracture provides a higher› permeability flow path for the oil or gas to reach the well bore compared to the permeability of the matrix of the surrounding subterranean formation. This higher-permeability flow path increases oil and gas production from the subterranean for› mation. 

[0009] A particulate for use as a proppant is usually selected based on the characteristics of size range, crush strength, and solid stability in the types of fluids that are encountered or used in wells. Usually, but not in all applica› tions, a proppant should not melt, dissolve, or otherwise degrade from the solid state under the downhole conditions. 

## Acidizing 

[001 OJ The purpose of acidizing is to dissolve acid-soluble materials. A treatment fluid including an aqueous acid solu› tion is introduced into a subterranean formation to dissolve the acid-soluble materials. In this way, oil or gas can more easily flow from the formation into the well. In addition, an acid treatment can facilitate the flow of injected treatment fluids from the well into the formation. 

[0011] Acidizing techniques can be carried out as acid frac› turing procedures or matrix acidizing procedures. 

[0012] In acid fracturing, an acidizing fluid is pumped into a formation at a sufficient pressure to cause fracturing of the formation and to create differential (non-uniform) etching leading to higher fracture conductivity. Depending on the formation mineralogy, the acidizing fluid can etch the frac› tures faces, whereby flow channels are formed when the fractures close. The acidizing fluid can also enlarge the pore spaces in the fracture faces and in the formation. 

[0013] In matrix acidizing, an acidizing fluid is injected from the well into the formation at a rate and pressure below the pressure sufficient to create a fracture in the formation. 

## Acidizing Sandstone or Carbonate Formations 

[0014] Acidizing is commonly performed in sandstone and carbonate formations, however, the different types of forma› tions can require that the particular treatments fluids and associated methods be quite different. 

[0015] For example, sandstone formations tend to be rela› tively uniform in composition and matrix permeability. In sandstone, a range of stimulation techniques can be applied with a high degree of confidence to create conductive flow paths, primarily with hydraulic fracturing techniques, as known in the field. 

[0016] In sandstone formations, acidizing primarily removes or dissolves acid soluble damage in the near-well› bore region. Thus, in sandstone formations acidizing is clas› sically considered a damage removal technique and not a stimulation technique. An exception is with the use of spe› cialized hydrofluoric acid compositions, which can dissolve the siliceous material of sandstone. 

[0017] Carbonate formations tend to have complex poros› ity and permeability variations with irregular fluid flow paths. Although many of the treatment methods for sandstone for- 

