Case Study 4 – Drop In Pigging Trials
Most mature offshore oil fields have extensive pipeline systems that have been in place since the assets were first developed, in many cases several decades ago. These pipelines may be inter-field gathering lines or pipelines between platforms. Ultimately, the product will need to be routed to shore via an export pipeline.
Recent developments in exploration technology now make it possible to discover and develop smaller reservoirs of hydrocarbons within the mature fields. In many cases the recoverable reserves are insufficient to financially warrant a dedicated pipeline to shore or even to the closest platform. In such cases, it might be viable to develop the new discovery by exporting the product to the closest pipeline system. Often the output of the new discovery will be comfortably handled by a small diameter pipeline e.g. 6” to 12” diameter.
If the small diameter pipeline is then tied into the closest existing pipeline, there will be a number challenges thrown up with regard to pigging:
- The cleaning pig for the new small diameter pipeline must be suitable for all bends, tees etc. present.
- The cleaning pig for the new small diameter pipeline must provide a good level of cleaning action.
- The pig must be able to “Drop In” to the mature pipeline with 100% success rate. The Drop In fitting might be a Hot Tap (possibly with a protruding lip) or a dedicated Tee.
- The pig must be able to be collected and pushed along the mature pipeline by the larger diameter pig. This will include going through bends, tees, wyes etc. that might be present downstream of the Drop In point and all the way into the pig receiver. This might involve some modifications or even a re-design of the large diameter cleaning pig.
Pigtek have now carried out feasibility studies and full scale testing for a number of Drop In scenarios including 6” into 14”, 10” into 24” and 10” into 24”/34”