Increase Stimulated Reservoir Volume SRV for Old Oil Wells in Changqing Oilfield

Abstract Changqing oilfield is a typical low permeability, low porosity sandstone reservoir, and most wells drilled in the field have to be fractured before production. Nevertheless, the fracturing scales were relatively small. With the number increase and rapid production decrease of old fractured well, study and application of re-fracturing technologies to restore or improve old oil wells productions become necessary. In this paper, we break through traditional re-fracturing ideas in sandstone reservoirs (such as old fractures re-extending or deflection fracturing), and put forward SRV fracturing technology to increase the stimulated reservoir volume by increasing fracturing scale, injecting base fluid / cross-linked fluid alternately, and using temporary plugging agents. Firstly, applicable conditions of this technology were studied, such as reservoir properties, rock brittleness, natural fractures and horizontal stress difference. Then, two kinds of temporary plug agents were selected and evaluated, also technological parameters and construction processes were optimized in lab. Finally, pre-fracturing evaluation of old oil wells was carried out and field tests of 3 wells were conducted. Field tests results showed that the selected plugging agents could realize temporarily plugging of the fractures by measuring downhole pressures. Microseismic fracture monitoring result indicated that SRV fracturing, by means of fluid alternate injection and plugging agent, could really increase SRV of the old oil well. After stimulation, average daily oil production of the 3 wells increased 72%. Laboratory researches and field tests results indicate that increase stimulated reservoir volume for old oil wells in low perm sandstone reservoir is technically feasible, and this technology has a good application prospect, which benefits the traditional re-fracturing methods significantly.