Research and Application of Temporary Blocking and Diversion Techniques for Fractures in Tight Oil Reservoirs

The tight oil reservoirs in the western region of Yanchang Oilfield are characterized by low porosity, low permeability, low pressure, and strong heterogeneity. During the process of volumetric fracturing, there are issues such as low complexity of fracture extension within single clusters and the inability to fully open multiple clusters within the same section. To increase the complexity of single-cluster fractures and improve the efficiency of cluster activation, a field test of temporary blocking and diversion volumetric fracturing was conducted on the Chang 72 layer of Well Luoping 29 and the Chang 8 layer of Well Ding 4994DX-1 in the tight oil region. The optimal dosage of the temporary blocking agent and the parameters for temporary blocking operations were determined. It is recommended that the amount of the temporary blocking agent be 150-250 kg per segment, with a displacement rate of 4-5 m3/min, and a blocking pressure of 2-3 MPa. The amount of temporary blocking balls should be 1.3 times greater than the perforation holes, with a displacement rate of 5-6 m3/min and a blocking pressure of 3-14 MPa. This led to the development of a temporary blocking and diversion technology suitable for tight oil reservoirs. Through the analysis of fracture monitoring data and fracturing operation curves, the construction success rate of temporary blocking and diversion was found to be over 80%, achieving the re-opening of fractures after temporary blocking and diversion. Post-fracturing performance evaluation indicated that Well Luoping 29 had an initial monthly cumulative oil production of 1206 m3 and an average daily oil production of 40 m3/d, which is 2.2 times the average daily oil production of neighboring wells at the same layer. Although the daily oil production of Well Ding 4994DX-1 was similar to that of neighboring wells, its daily fluid production and wellhead pressure were increased by 1.0 times compared to neighboring wells, showing better post-fracturing performance. The successful trial of the temporary blocking and diversion technology provides significant technical support for the thorough stimulation of tight oil reservoirs.