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Debottlenecking a natural gas field's gathering system and centralizing the compression probably are the most economical ways to make sure every cubic foot of gas, no matter what the bottom-hole flowing pressure, gets a chance to pass through the sales meter.
As North American gas producers continue to squeeze every economic cubic foot of natural gas from the ground, the push continues for lower flowing bottom hole pressures.
At the same time, the trend in low-permeability reservoirs has been decreased well spacing, resulting in a large amount of infield drilling. The increased infield drilling, combined with improved hydraulic fracturing techniques, has allowed many of these new wells to initially produce at high rates relative to the older wells in the same reservoir. The end result is a new well producing 2 MMcf/d coming into the gathering system and knocking off 1 MMcf/d of production from older wells. The net result at the `cash register' is a production throughput increase of 1 MMcf/d. If the economic case for the project was not run on that projected increase in production of 1 MMcf/d, "Houston, you have a problem!"
Cause Of The Problem
When a new field is discovered or a new area of an existing field is opened for development, bottom-hole pressures are high and life is good. With shut-in tubing pressures in the thousands of pounds per square inch (psi) and pipeline pressures in the hundreds, the last thought is, "What will happen when this line pressure is pulled down to 45 psi?" The end result is gathering systems with significantly undersized pipe in place not allowing field pressure to be reduced efficiently.
A quick and easy solution is to install wellhead compression or multiple smaller stations close to the wells, resulting in gathering systems with "lots of moving parts." The system will work and the older wells are able to produce with the stronger wells, but it may not be the best way to solve the problem.
Consequences Of The Problem
Mike Cormier, East Texas Team Leader with BP America, put it best: "We can dedicate our capital to drill a successful well or have a great recompletion. However, the net effect is that only the gas making it to the 'cash register' counts." Cormier...