Effect of wormholing on the fluid loss coefficient in acid fracturing Conference Paper uri icon

abstract

  • In most acid fracture designs, a leakoff model developed for proppant fracturing is used to calculate the acid volume lost into the formation. Since wormholing in acid fracturing results in a few large channels near the fracture, the leakoff velocity of the fracturing fluid can be higher in acid fracturing than in proppant fracturing. This paper presents a new leakoff model including the effect of wormholing on the overall fluid-loss coefficient. The leakoff model is based on a volumetric model describing wormhole growth in acid fracturing. Conveniently, the leakoff velocity based on the volumetric model for wormholing is still inversely proportional to the square root of treatment time. Laboratory coreflood results are presented which support the use of the volumetric model for the linear flow region near the fracture walls. The results of the model show that the overall fluid-loss coefficient depends strongly on the number of pore volumes required for wormhole breakthrough in a coreflood. A large number of pore volumes to breakthrough means a slow wormhole growth rate, which more commonly occurs in dolomite compared with limestone. The effect of wormholing on the overall fluid-loss coefficient is insignificant in acid fracturing of dolomite. However, for limestone, the number of pore volumes to breakthrough is small and wormholing increases the fluid-loss coefficient significantly, especially for a gas well. An example in the paper shows that the overall fluid-loss coefficient can be over 100% higher because of wormholing in a typical case for a gas well in a limestone formation.

published proceedings

  • Proceedings of the SPE Latin American and Caribbean Petroleum Engineering Conference

author list (cited authors)

  • Hill, A. D., Zhu, D., & Wang, Y.

complete list of authors

  • Hill, AD||Zhu, D||Wang, Y

publication date

  • January 1994