Settable, form-filling loss circulation control compositions comprising in situ foamed non-hydraulic sorel cement systems and method of use

Abstract

This document relates to settable, non-hydraulic foamed cement compositions comprising nitrogen gas-generating compositions used for loss circulation control.

What is claimed is: 
     
       1. A foamed cementitious composition, comprising:
 magnesium oxide (MgO); 
 a salt selected from the group consisting of magnesium chloride (MgCl 2 ), magnesium sulfate (MgSO 4 ), ammonium hydrogen phosphate (NH 4 H 2 PO 4 ), and hydrates thereof; 
 a nitrogen gas-generating compound; 
 a foam surfactant; and 
 an oxidizer. 
 
     
     
       2. The composition of  claim 1 , wherein the salt is magnesium chloride hexahydrate (MgCl 2 .6H 2 O). 
     
     
       3. The composition of  claim 1 , wherein the foam surfactant is selected from the group consisting of an alkyl sulfate salt with a C 12 -C 14  carbon chain, a betaine, and a hydroxysultaine. 
     
     
       4. The composition of  claim 3 , wherein the foam surfactant is cocoamidopropyl hydroxysultaine. 
     
     
       5. The composition of  claim 1 , wherein the nitrogen gas-generating compound is an azo compound. 
     
     
       6. The composition of  claim 5 , wherein the azo compound is azodicarbonamide. 
     
     
       7. The composition of  claim 5 , wherein the azo compound is about 1% to about 10% by weight of the MgO. 
     
     
       8. The composition of  claim 5 , further comprising an amine activator selected from the group consisting of carbohydrazide (CHZ), tetraethylenepentamine (TEPA), and hydrazine sulfate. 
     
     
       9. The composition of  claim 8 , wherein the weight ratio of the azo compound to the amine activator is about 5:1 to about 1:5. 
     
     
       10. The composition of  claim 8 , wherein the amine activator is CHZ. 
     
     
       11. The composition of  claim 1 , further comprising a set retarder selected from the group consisting of hexametaphosphate, sodium borate, sodium citrate, citric acid, and an aminophosphonate. 
     
     
       12. The composition of  claim 1 , further comprising a viscosifier. 
     
     
       13. The composition of  claim 1 , wherein the pH of the foamed cementitious composition is greater than about 4.