Abstract One of the more important aspects of any fracturing treatment is the proppant that is used. In some instances, particularly in deep well applications, the type of proppant used can make a difference between the treatment being an economic success or failure. As job size increases, the price of the proppant becomes a significant percentage of the proppant becomes a significant percentage of the overall treatment cost. This is especially true if the various high strength proppants are to be used. This paper deals with a fracture permeability study of many of the available low and high strength proppant materials. In each case, fracture proppant materials. In each case, fracture permeability is measured as a function of closure stress. permeability is measured as a function of closure stress. Using the apparatus described in this paper, the relative permeabilities of each proppant are obtained using identical testing procedures. Many current treatments incorporate both frac sand and one of several more expensive high strength proppants. For this reason, special emphasis is placed on test results obtained from mixtures of the high strength proppant and the more economical frac sand. proppant and the more economical frac sand. To illustrate the effect that various proppants or proppant mixtures have on the results obtained from a fracturing treatment, a computer analysis is made. The analysis will indicate the effect of fracture permeability on estimated production increase and the effect of proppant choice on the economics of the treatment. From this analysis and the permeability data reported, guidelines for the choice of a permeability data reported, guidelines for the choice of a proppant or mixture of proppants are set up for proppant or mixture of proppants are set up for shallow, medium and deep well application. Introduction The use of hydraulic fracturing, as a method for increasing well production, has risen significantly in recent years. This trend will continue as it becomes increasingly important to maximize the amount of oil or gas that can be produced from a given well. In the past, most pre-job planning centered around decisions concerning the type of fracturing fluid to be used or the pump rate and treating pressure to be encountered. Little, if any, time has spent on the choice or combinations of proppants to be used. As treatment costs rise, increased design time is being spent on all aspects of the treatment. Until recently, there have been relatively few significant changes in the proppants used in hydraulic fracturing. By far the most common proppant consists of a specially screened, high grade sand (usually 10–20 or 20–40 mesh). As well depths increased, it became apparent that higher strength proppants were required. The first such proppant to proppants were required. The first such proppant to gain widespread use was glass beads. Recent advances have resulted in the development of the new sintered bauxite proppant. In order to take full advantage of all the available proppants, it is necessary to determine certain well parameters, in particular, the amount of closure pressure exerted by the fracture faces on the proppant. Once this value has been calculated, the proppant. Once this value has been calculated, the permeability of the proppant at reservoir conditions permeability of the proppant at reservoir conditions can be evaluated and the economics of the treatment and its results estimated. Presented in this paper are the relationships between fracture permeability and closure pressures for the following list of proppants:10–20 and 20–40 Hickory Sand (Heart of Texas or San Saba frac sand)20–40 St. Peters Deposit (Ottawu or Gopher State frac sand)12–20 and 20–40 Glass Beads20–40 Sintered Bauxite100 Mesh Sand (Oklahoma #1)Mixtures of Hickory Sand and Glass Beads