system.The first problem that was encountered was unexpectedly severe gumbo in the first 500 feet of 12- 1/4 inch hole. This had not been reported often by the other operators. This caused flowline plugging, flow splitter plugging, and screen blinding. The problem was largely avoided by changing the drill out mud from a hole-cleaning rheology to simply water.
GN Solids Control Manufacture Mud Processing systems.
(http://www.gnsolidscontrol.com)
The gumbo was dispersed by the water, and plugging problems were reduced. By the time the gumbo zone was passed, it had created a clay-laden native mud, which was used successfully in the rest of the section after treatment. The auger flights in the auger tanks were also easily
packed off by the sticky gumbo clay that was drilled in the upper 12-1/4 inch hole. This resulted in the need to shut down the augers and clean them out. To avoid this, the auger tanks were replaced by simple four-sided rectangular tanks. A backhoe is used to move the dried
cuttings from the tanks to the dump trucks. With the large screen area of four flow line shakers, it was found that 84 or 110 mesh screens can be run without appreciable mud loss in both the intermediate and production hole sections. This is in contrast to the other operators who typically run 20 to 40 mesh screens on two or three flow line shakers. It is not known if the
improved operation of the shakers is due to less sticky crude oil at Hamaca or to the larger screen area.
(http://www.gnsolidscontrol.com/
Solids control technicians are required to watch the shakers at all times. Screens are washed with highpressure water spray on connections, and occasional overloading of the shakers must be managed. Due to the relatively large size of the formation sand grains, a large majority of drilled solids are taken out by the shakers. Consequently, it has been found that only one set of desanders needs to be run.
The mud cleaner, which is a 20-cone desilter above a linear shaker, was not performing efficiently at first. The head provided by the centrifugal pump at the feed header was too low. Rather than change the pump impeller or speed to increase the feed head, four of the
desilter cones were blanked off in an attempt to reduce flow and increase feed head. This action resulted in increased head at the feed header and improved the cone discharge. It was found that 16 cones provided sufficient treatment capacity to maintain the mud in excellent condition.
It has also been found that running a slightly coarser screen on the mud cleaner, a 150 mesh instead of a 210 mesh, is advantageous. With coarser screens, the desilter cone bottoms can be opened up to make a finer cut, discharging more liquid and removing more solids. The additional solids that pass through the screen are easily removed by the centrifuges.
(http://www.gnsolidscontrol.com/
Two centrifuges are fed from compartment #4, which catches the mud cleaner screen underflow and receives additional clean mud from the desilter discharge compartment (#5). With these two units processing concentrated solids from the mud cleaner, it has been
found that mud weights of 8.5 to 8.6 ppg can be maintained without dilution. These centrifuges tend to discharge little solids when drilling pure pay sand, but they discharge a large amount of solids when a clay is drilled in the intermediate hole, or when a shale is encountered in the production hole
