No abstract

Formation of cisphultic sludge during acid ,stinlli[a~itjtt Iurs been a serious probletn in many areas for' several years. Recent studies have shown that sludge ntay ako aflect resu]ts in many areas where it has not yet been recognized as such, These studies indicate that: (1) sludge is a precipitate of colloidal materiqls present in crude oil;(2) the precipitates occur due to changes in environ- mental" conditions of ihe crude by addition of material.r sucIi as acid; (~) on~e formed, sludge is insoluble in most treating chetniral,s; and (4] sludge can be prevented or controlled by use of stabilizing agents in treating fluid or by use of certain solvents as the outer phase Of acid-in-.. oil enndsions, 1The purpose of this paper will be to show how and why sludge is fotwed and ito w it can be prevented or controlled. Simple laboratory tests to determine tile probability of sludge formation prior to treatment are discussed.

HydrojIuotic-hydrochloric acid mixtures have heen successfully used to stimulate sandstone reservoirs for a number of years. Hydrofluotic acid (HF) has a specific reactivity with silica which makes it more efleclive than HC1 jor use in sandstone. Kinetics of the reactions of HF have been studied to determine the related effects of reservoir composition, temperat::m, acid concentration and pressure on the spending ra~e o~HF. Secondary eflects from by-product formation are noted and described, Predictions are made concerning the improvement in productivity resulting from HF treatment of skin damage.The kinetic order of HF reaction in sandstone was experimentally determined to be first order, i.e., the reaction rate is proportional to concentration. HF reacts faster on calcite than on clay, which, in turn, is faster tiran the reaction rate of HF on sand. Static conditions, retard the HF reaction rate. As HF is forced into cores, there is a temporary reduction as a function of flow rate atrd acid concentration,Extensive deposition of calcium f iuoride in acidized cores was not observed. Although some CaF* was detected, it wb.s not considered a major source of damage in cores containing moderate amounts of carbonate. Other fiuosilicates could be potentially more dangerous than CaF, in reducing permeability.

No abstract

The one-electron oxidation and reduction processes for some 80 dithiocarbamates of Cr, Mn, Fe, Co, Ni, and Cu reveal a marked dependence of redox potential on the metal 3dn electron configuration. For all the complexes examined, the relative ordering of the redox potentials with the dithiocarbamate substituents is remarkably consistent for both oxidation and reduction processes.