The chief objectives of this investigation were to study, theoretically and experimentally, the sweep efficiency and oil recovery for steam injection into a five-spot pattern. Experimental runs and mathematical simulations were conducted for this purpose. The experimental models used consisted of glass bead packs simulating a quadrant of a five-spot pattern, over-lain and underlain by heat-conducting formations, and fitted with thermocouples to determine the temperature distribution during the steamflood. Effects of oil viscosity, saturation, injection rate, and heat losses on oil recovery and sweep efficiency were studied.The mathematical model developed was a combination of the concept of flow in channels and a formation heating model, allowing for a variable injection rate, differences in the properties of the overburden and the underburden, and variations of relative permeabilities with temperature. The mathematical model was used to simulate the ex-perimental runs. Good agreement was observed. It was found that, for the oils tested, sweep efficiency in steam floods was 40 to 50 per cent, depending chiefly on th; viscosity of the oil used. The oil recovery, however, was large, being of the order of 80 per cent, because of the hot waterflood ahead of the steam zone. The sweep effr ciency was relatively insensitive to initial saturations and the steam injection rate. Formation thickness and steam quality were found to have an appreciable effect on oil recovery. For low-quality steam, the ,-steamflood degener-ates rapidly into a hot waterflood. ADAFEL C. RINCON is ebief of the reservoir studies group in the Ministry of Mines and Hydrocarbons of . TIIE PAST FEW YEARS, pattern steamflooding has gaine(I considerable popularity as a secondary or tertiary oil recovery method for both viscous and lowviscosity crudes. Currently, however, few methods for calentating-oil recovery by a steamflood are available.Marx and Lagenheim and Willman et al. 1 2 1 did pio-neering work in this area by proposing mathematical models for calculating the volume of the formation heate(i an(i the oil recovery from a radial steamflood. Davies, Silberberg tnd Caudle proposed a method for I)redicting oil recovery from a five-spot steam-flood, bastd on the approximation of the streamlines by straiglit lines radiating from the injection well, and then (converging to the production well. The I)res-ent Nx-ork ])roposes an improved method for predicting the ])erformance of a steamflood in a five-spot pat-trn, Lisin,, a combination of Higgins and Leighton's"', Marx and. Langenheim's Willman et al.'s"', and Ramey's techniques adapted for a steamflood in a five-slot pattern. Also, extensive experimental results are liserited, designed to test the model, and also to obtain data on pattern steamflooding, with regard to oil viscosrLy, distillability, injection rate, ete. Fair to good agreement was obtained between the model pre-(nctit)ns and the experimental results. On the whole, it wis found that the sweep efficiency in a five-spot steamflood is consi...