The Effect of Fluid Loss on Fracture Extension

Abstract

Abstract Field trials have shown that superior fracturing treatments may be obtained when a low fluid loss oil is employed as the sand carrier. Such a carrier now can be made very economically from lease crude oil by the use or a fluid loss controlling additive. Experimental fracturing tests were conducted to determine the relative importance or fluid loss and viscosity in fracture extension. It was found that sand concentrations as high as 8 lb or sand per gallon could be displaced into the formation at a 4 bbl/minute pumping rate using a treated lease crude of low viscosity (12 cp) and low fluid loss. During another test 48,000 lb or sand at 4 lb/gal were displaced using the same treated crude and pumping rate. Other field tests have indicated that low fluid loss, low viscosity fluids may be successfully used where high fluid loss, high viscosity fluids are not effective. These results demonstrate the importance or fluid loss control in fracture extension. The importance of low fluid loss is rapidly being recognized by the industry. Hundreds or wells have been fractured using lease crude with a controlled fluid loss. Fewer sand-outs are encountered and production increases tend to be more sustained. The converted oils have performed very well in formations that have been difficult to fracture in the past. Such rotations include chats and conglomerates and reservoirs with temperatures in the 200°F to 300°F range. Both laboratory and field results have shown that crudes treated to reduce the fluid loss are fully compatible with the various gelling materials now available. The very low fluid loss gel that results from this combination is advantageous in many instances. With proper treatment design, the selection of crude oils is now almost unlimited. The development or the hydraulic fracturing process has occupied only a few years in the history of the oil industry. During this brief period, however, fracturing has become the major method for production stimulation and its application has led to the reopening of many oil fields formerly classed as depleted.