Mechanism of migration and settlement for temporary plugging ball in shale gas horizontal wells

Abstract

In order to determine the migration and settlement mechanism of temporary plugging balls in horizontal wells, the rules for distribution, migration and settlement of balls in different location were researched through calculation, coupling fracturing fluid and characteristics of movement based on CFD (computational fluid dynamics), DEM (discrete element method) and DDPM (dense discrete phase model), and the intensity, plane and spatial distribution of the microseismic events before and after ball-addition were analysed. The results showed that: First, the central flow core in the pipeline is the main migration carrier of the temporary plugging balls and proppants, low-viscosity liquid performs differences when inflowing at various perforation holes. The settlement and plugging in downstream cannot be effectively improved while the upstream without balls’ settlement. Second, due to the fluid resistance, the mean velocity of temporary plugging balls decreases and balls spread along the casing wall while the interaction force can be ignored. Under different displacement, the temporary plugging balls’ migration speed has a relatively stable value, the displacement of 5 m3/min is the critical value for the effective setting of temporary plugging balls. Thus, most of the micro-seismic events after ball-addition were concentrated in the upstream clusters, the impact scope of the micro-seismic events of 6-clusters is greater than that of 8-clusters perforation. After ball-addition in 6-clusters, the key effect is to improve the complexity of the microfracture network, while in 8-clusters to improve SRV (simulated reservoir volume) for the beginning first 4 clusters. So that is, increasing the number of clusters will lead to an inadequate microfracture length extension and only SRV (simulated reservoir volume) near the wellbore zone was improved.

Temporary Plugging Agent System for Thermally Induced Phase Change Fracturing in Shale Gas Reservoirs

“…Generally, a remote delivery device needs to be installed separately during the construction of the temporary plugging ball, and it needs to be delivered manually. Moreover, the migration distance of the temporary plugging ball fracture is short of the formation, and most of it acts on the fracture opening or in the middle. − Most of the common gel-type temporary plugging agents use a gel breaker to break the gel. , This gel breaking method causes great damage to the reservoir, and the gel breaking time should not be controlled. , The autonomous thermal degradation of the gel at reservoir temperature is the development trend of the gel temporary plugging agent. Compared with the temporary plugging ball, the supramolecular gel temporary plugging agent can simplify the construction method, and by entering the far end of the fracture to achieve temporary plugging in the deep part of the fracture, it can improve the construction efficiency, increase the complexity of the fracture, and prevent well channeling.…”