|dc.description.abstract||Today, optimizing well stimulation techniques to obtain maximum return of
investment is still a challenge. Hydraulic fracturing is a typical application to improve
ultimate recovery from oil and gas reservoirs. Proppant fracturing has become one of the
most widely considered alternatives for application in carbonate reservoirs. Especially in
areas that have high closure stress, the non-smoothly etched surface created by acid
fracturing may not remain open upon closing, resulting in decrease in fracture
conductivity and unsuccessful stimulation treatment.
In early years, because of the increase in the success of proppant fracturing,
proppant partial monolayer has been put forward as a method that helps generate the
maximum fracture conductivity from proppant fracturing treatment. However, this
method was not widely successful because of proppant crushing and proppant
embedment problems that result in losing conductivity. The ability to transport propping
agents in available fracturing fluid was also poor and resulted in difficulties and failures
to obtain proppant partial monolayer placement. For carbonate formations, acid fracturing is another effective stimulation method. Simpler operation and lower cost
made the technique attractive in the field with plenty of successful experiences. The
heterogeneity feature of carbonate formation brings a challenge to create sufficient
conductivity. In cases of high closure formation, fracture conductivity is hard to sustain.
This factor limited the applications of acid fracturing sometimes.
In this study, laboratory tests were carried out using low concentrations of ultralightweight
proppant to obtain partial monolayer proppant. Because of low specific
gravity property of this proppant, it was claimed to help improve proppant transport
inside the fracture.
In this experimental study, the partial monolayer technique was examined with
particular emphasis upon the impact of acid in possibly improving fracture conductivity
of carbonate rocks. The technique is referred as "closed fracture acidizing". After
obtaining a partial monolayer distribution on the fracture face, gelled acid was injected
through the fracture face. Fracture conductivity before and after acid injection were
Experimental results showed clearly that acid injection does not enhance fracture
conductivity of partial monolayer proppant fracturing. The more the volume of acid
injection, the more rapidly fracture conductivity declines.||en