Proppant spit back control technology field test

Conventional hydraulic fracturing wells into production processes and problems
In recent years, Jiangsu Oilfield  Hydraulic fracturing  has gradually become the main stimulation, fracturing stimulation measures yield reached more than 80%. In the fracturing process, the fracturing fluid flowback timely, largely determines the magnitude of stimulation effect after pressure. Therefore, it is possible to improve the discharge rate, such as swabbing grab row, large pump pumping faster and so on.
For complex fault block Jiangsu Oilfield, formation pressure coefficient of 0.6 or more wells, more than 70% of the construction wells are present more serious phenomenon of  Proppant  spit back. With the fracturing fluid flowback and production pressure increases, the portion of the proppant has also been brought into the wellbore, brought many problems. Mainly in the following four aspects: ① spit back part with proppant flow into the pump cylinder, causing the pump stuck, causing pump inspection, not only increase job workload and delays fracturing fluid flowback timing. ② For shallower pockets fracturing wells, proppant spit back period will result in the discharge of sand buried reservoir, the need for sand washing operation. Usually about 2000m sand flushing pump inspection operation cycle takes 2 days to 3 days, and sand washing operation during normal working media intrusion, increasing the workload of the drain, so will seriously affect the  fracturing  effect. ③ proppant spit back propped fracture can cause narrowing, causing fracture conductivity decreased, so that the effect of fracturing stimulation affected.

If the majority of near wellbore proppant spit back will cause cracks completely closed, causing fracturing fail. ④ normal production process, as well construction the amount of proppant pumped back discharge displacement is proportional to the increased production parameters over general proppant spit back, shortened production period, the smaller the operating parameters taken limit oil production, inhibits The production capacity of the well construction.
Based on the above, in order to control proppant spit back, try to play a fracture stimulation ability to extend validity measures, we carried out a controlled process of  Proppant  spit back, after field application has been successful.

Spit back control proppant technology research
Jiangsu Oilfield hydraulic fracturing process, the general use of the particle size of Φ0.45mm ~ 0.90mm ceramic as proppant, drawing wire wrapped screen gravel pack sand control technology. Through a look-up table can know: the slit width of 0.3mm laser slotted tube (its size reference slotted slotted liner sand techniques to determine) down to the fracturing layer can control the amount of proppant spit back, depending on column length), the fracture stimulation effect is not affected. Therefore, in the wells after hydraulic fracturing can be composed by laser slotted tube control proppant column spit back into the well, is on the fracturing layers, supported on the surface of the sand aside, aside from the sealing tools to achieve and packer annular space. Well production, a small amount of proppant flow into the wellbore with the output being blocked laser slotted tube in the annular space, the gradual accumulation of great ability to form sand flow barrier, in order to achieve control of proppant back to vomit.

Key technology
① supporting the development of sand column, effective control of proppant spit back into the wellbore, the lateral column formation flow area to meet the needs of production capacity and easy to salvage, without prejudice to future work on other measures on the production floor. ② short construction period, in order to facilitate timely fracturing fluid flowback to ensure that oil does not cause secondary pollution. ③ sand filling process must be matched, proppants have headroom to meet the requirements of the formation of sand barriers.
2.2 Column Portfolio Selection
2.2.1 Integration of anti-spit back proppant column (Figure 1) consists of sealing tools, telescopic tube, slotted tube, centralizers and other components. By suppressing packer sealing tool to achieve sealing the annular space, and the column reserved for the well. Consider fracturing a limited period in order to facilitate other measures to carry out oil well in the future, follow the simple construction, easy to salvage the principles of the design of the column, by starting out small repair downhole string. According to column length, the lower end of the short slotted tube plus Flip becomes silk, achieve column-by-pole fishing.
2.2.2 slotted tube and process parameter selection based  Fracturing proppant  particle size used was designed by the slit width 0.3mm, length 200mm straight stitch seam laser slotted tube, single length determined according to reservoir thickness (generally use 2m).
2.2.3 The choice of tools seal sealing tool seal member and lost mainly by hand components, through pressure from the tubing packer, seal oil jacket annular space, but aside downhole string.
2.2.4 Development of supporting tools A. compensation device: lifted the seal tool requires a certain itinerary designed compensation device, ensure the sealing tool successfully reopened. Compensated by the expansion of its main chamber and cut pin composed of sand when the downhole string was buried after death, cut the dowel through the upper lift the load, since the sealing tool. B. centralizer: righting block consists of nylon processing, maximum diameter of 120mm, and can rotate freely. By installing the centralizer column to ensure column centered, so that uniform proppant accumulation in the annular space.
2.2.5 Process of determining downhole sand surface A. Selection: To ensure the normal output of the reservoir, while downhole string not too long, for future salvage work to bring trouble to design sand surface in the reservoir bottom boundary 2m; B . Setting the number of slotted tube: According reservoir thickness determines kerf lengths to ensure the flow area, to meet production requirements.
2.3 supporting the choice of sand filling process
????Sand filling construction, sand ratio increases, the end of high sand ratio (generally 50% to 60%), the conditions are right for some wells due to replace the implementation process. As near wellbore sand ratio, crack closure, it will support the formation of a high slit width, put into operation, a little spit and back proppant sand barrier formation, will not cause crack closure, affecting the yield.

3 Field Test and Effect Analysis
W19 wells in July 2003 for hydraulic fracturing, venting and make sand washing operation, from the washed sand fracturing string, spit back under control proppant column, is to suppress the packer sealing tool that will set aside column in the well, and then promptly put into production. After fracturing, with the same size G1-3A fracturing wells (September 2003 construction) compared in Table 1, Table 2, two wells are used due to fracturing replacement process, but the G1-3 well fracturing, Sand washed directly after the pump operation, did not implement process control proppant spit back. G1-3A wells produce water that is not 18 days, check the pump sand surface probe, up 110m (the amount of sand 1.33m3), resulting in oil sand buried by sand washing pump inspection operations before resuming production due to sand card comparison table sand buried oil wells and other reasons continuous operation four times. From the production point of view, W19 wells fluid from the 1.4t / d up to the press after the initial liquid production 9.9t / d, to the current fluid production 7.3t / d, from the initial production after fracturing   until now production has been stable, produced fluid tracking tests showed no sand phenomenon. G1-3A well fracturing initial oil production up to 8.1t / d, the sand buried reservoir, check fluid production only after the pump 4.9t / d, and production plummeted, analysts believe that the proppant spit back a lot, resulting in near-wellbore crack closure, it is difficult to ensure fracturing effect, seriously affected the normal output of oil wells. From the economic point of view, the process column one-time investment 40,000 yuan / wells, wells to avoid a punch sand pump inspection operations to recover the costs.
4 Conclusions and understanding
Field application, confirmed that the technology mature and feasible, only a small investment, and the construction is simple, spit back the control proppant has good targeted, has good application prospects.