On November 27th, 2009, the operation of coiled tubing sand flushing under negative pressure was accomplished in the Guang¡¯an X well of the AntonOil Company, which offers us not only a new process design for the capacity recovery of low pressure wells, but also an effective solution to the subsequent development of the low pressure sandy gas wells.
The Guang¡¯an X well is a high-inclination well with a max gradient of 53º, a well depth of 2005 meters, and an artificial well bottom depth of 1988 meters; Besides that, this well is also a perforated well which produces sand heavily after sand fracturing. As a result, the well bore below 1903 meters is buried by sand and sand content in the well is 1.1m; the reservoir pressure is 8 MPa, and the reservoir pressure coefficient is only 0.4. The daily gas output is 0.5¡Á104 m3 with intermittent production before sand flushing operation.
Because reservoir pressure of this well is low and the leakage of flushing fluid is serious, two conventional sand flushing operations have both failed due to the failure of building a normal cycle. There are several difficulties in sand-flushing operation for such a formation with low pressure and high fluid leakage: 1. Low formation pressure and serious leakage make it hard to set up a normal cycle with a conventional sand flushing operation; 2. during the process of sand flushing operation, with the increasing exposure of the producing pay, the leakage of sand cleaning fluid will heavily pollutes the reservoir; 3. It¡¯s difficult for the sand cleaning fluid to carry sands out in high-inclination wells. Against the sand flushing issue, the technicians of AntonOil Company, after precise calculation, proposed a new solution with the technology of the coiled tubing imbalanced sand flushing under negative pressure. They developed a special sand flushing tool, and utilized a kind of sand cleaning fluid with low-damage and strong carrying capacity, and auxiliary facilities with a simple surface process. With this application, elimination operation of 83m sand column could be finished in only 3.5 hours from 14:00 to 17:30 on November 27th. There was nearly no leakage of sand cleaning fluid during the operation. The gas production doubled after sand flushing operation and the continuous production was realized as well.
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