When a well is completed, it must be cleared of sand before it’s production can be lined up to the collection laterals. This is accomplished by “flowing-back”, or “flaring”, the well. For a typical gas well, this requires venting the tubing to the atmosphere for 3 or 4 days at a typical rate of 5 MMSCFD. To avoid wasting $50,000 worth of natural gas, a portable sand separator may be installed between the wellhead tree and the permanent production equipment. While portable sand separator skids may be rented, a sketch has been provided in figures 2-3A and 2-3B for those producers who may wish to build their own unit.
Towards the end of a well’s life, it should probably be placed on an intermittent type operation as described in the previous chapter. This will keep the well from loading up with liquids. As time goes by, the back-pressure from the collection lateral will be too high to permit the entrainment velocity (or flow point) to be achieved when the well is opened-up, even though it has been shut-in for many days. Under such circumstances, the well must be flowed-back to the atmosphere. Addition of a few soap sticks through the wellhead cap twenty minutes prior to venting the well to the atmosphere (really to a pit to contain the brine that will be blown out) is a good procedure. Figure 2-4 illustrates the piping configuration at wellhead required to routinely acomplish the above. It may take 15-30 minutes to successfully blow the brine out of a tubing string. If the procedure is working, the wellhead pressure will climb as the slugs of brine pass up through the flow-back connection. Of course, once a well has declined to this point, installation of wellhead compressor or downhole corrective measures are appropriate.
