Limited-entry fracturing (LEF) technology is a widely used method to realize the simultaneous propagation of multiple fractures in horizontal wells. The key of this technology is to create high perforation friction to maintain the high treatment pressure in the wellbore and realize the uniform fluid entry of multi-fractures; however, high perforation friction cannot be effectively maintained due to the serious perforation erosion effect. Considering that the current laboratory studies mostly used small fluid injection flowrate, low injection pressure, and small proppant dosage, this study has developed a field-scale flow system to investigate the effect of various factors on perforation erosion under real field conditions. The filed-scale flow system uses the real fracturing trucks, proppant, and perforated wellbore, the fluid flow rate through perforation could reach 200 m/s and the injection pressure could reach 105 MPa. The effects of different parameters, such as injection flow rates, proppant concentration, proppant type, proppant size, and carrying fluid viscosity, on the perforation erosion were investigated. The experimental results show that: (1) The perforation friction during erosion goes through two stages, i.e., the roundness erosion stage and the diameter erosion stage. The reduction of perforating friction mainly occurred in the first stage, which was completed after injecting 1 m3 proppant. (2) After erosion, the perforation changes from the original circular shape to a trumpet shape, the inner diameter is much larger than the outer diameter. (3) The more serious perforation erosion is caused by the conditions of high injection flow rate, large proppant size, using ceramic proppant, and low viscosity fluid. The findings of this study can help for a better understanding of perforation erosion during the limited-entry fracturing in the horizontal wells, and also could promote the establishment of a theoretical model of perforation erosion under the field-scale conditions.

Conglomerate reservoirs often exhibit chaotic internal structures and strong heterogeneity due to the influence of gravel, which seriously restricts the balanced initiation of multiple clusters and the balanced expansion of artificial fractures in the volume fracturing section of horizontal wells. Therefore, clarifying the distribution pattern of gravel in conglomerate reservoirs is of great significance for the design and parameter optimization of horizontal well segmentation and clustering. This work conducts research on the interpretation results of imaging logging, establishes a characterization model for the distribution characteristics of gravel around horizontal wells, develops gravel feature recognition and analysis software for conglomerate reservoirs using image processing technology, and effectively obtains the morphology of gravel in imaging logging. Based on this, a correlation model between conventional logging and imaging logging is constructed to predict the distribution of gravel in horizontal wells without imaging logging. Using the Kriging interpolation method, a “point line surface” gravel distribution prediction method is proposed. Through three methods of imaging logging, downhole eagle-eye camera, and on-site coring, the model accuracy is found to be greater than 80%, guiding segmented clustering to avoid high gravel areas. During the fracturing process, the wellhead pressure is lower than that of adjacent wells, enabling greater fluid savings per well. The production effect is better than that of adjacent wells in the same block, providing a reference for the study of gravel distribution characteristics in conglomerate oil reservoirs.

Because it provides favorite ancillary support in terms of technology research and tools test, full-scale simulator for Drilling and Producing is still the focus for overseas researches. The test capability for full-scale simulator represents the level of development for national petroleum exploration and development. That the increasing efforts on unconventional oil & gas and deep water exploration brings new challenges to theory and technology for oil-gas exploration, so the full-scale simulator provides an intermediate bridge for theory and technology innovation. Following the tracks of the development of full-scale simulator, the overseas and domestic classify and development of full-scale simulator was analyzed, and identifying the main technical bottlenecks faced during it establish. This paper describes the development of key technologies for wellhead loading system, wellbore simulation technology and test monitoring system. On this basis, the research prospect for the full-scale simulator was forecasted.