M.D. PAKHOMOV, N.S. MARKOVA, M.M. MUKHIN, Gubkin Russian State University of Oil and Gas

 

The laboratory “Drilling mud surfactants and acid systems for oil production” of the Institute of Field Chemistry at Gubkin Russian State University of Oil and Gas conducted original researches of dissolvability of proppant ForeProp (fraction 16/30) in various acid compositions.

 

In order to define the dissolvability of proppant ForeProp (fraction 16/30) 2 g of proppant, weighed to a precision of 0.0001 g was placed in a lidded teflon glass and heated up to the test temperature. After that the estimated amount of acid, heated up to the test temperature, was added. The amount of acid should acid the numerical value of the surface area of the tested proppant by 2.5 times. In order to define surface area of the proppant, the length of proppant particles evenly lined to a precision of 0.1 mm was measured. The particles of the proppant are believed to have the form of a globe. On the basis of the number of the particles the diameter of one particle was calculated. Then they defined the area of its surface and the area of surface covered by all measured particles. Knowing the surface area of the measured particles, we could calculated the surface area of the proppant weigh, taken for the test.

 

The proppant was exposed to the impact of acid compositions under the estimated temperature (60 °С and 80 °С) during 2 and 8 hours. After that the proppant weigh was filtered through a filter of constant weight and washed by purified water in

the amount of at least 250 ml. After reaching the constant weight of proppant filters the amount of proppant dissolved by the acid was calculated.

 

The obtained data are supplied in Figure 1.

 

Figure 1 suggests that mud acid has the highest activity. Yet, the dissolvability of proppant in mud acid under the temperature of 80 °С and exposure during 8 hours is lower than under the temperature of 60 °С. This is explained by the formation of secondary precipitation. Gravity method was applied in the researches and secondary

precipitation increased the mass of proppant after the test. Secondary precipitation after dissolving proppant in mud acid is shown at Figure 2.

 

Conclusions. Mud acid shall in no way be used for well stimulation after HF. The probability that proppant will be dissolved in 12% hydrochloride acid is also very high. The use of working solutions of acid compositions “Khimeko-TK-2” and “Khimeko SK TK-4” is more preferable.