GB1420011A - Method and apparatus for separating material leaving a well - Google Patents

Abstract

1420011 Separating oil from water U FAVRET JNP 9 Jan 1973 1218/73 Heading B1D Water contaminated with oil, produced at an offshore oil well, is purified by passage down a zig-zag path defined by inclined baffles 18 in a partially submerged column 12, the underside of each baffle defining an oil-collecting zone 34, prior to being discharged from the bottom of the column into the surrounding sea, flow being intermittently stopped or at least reduced to allow coalesced oil globules to rise into zones 34. In Figs. 1, 2 water enters the top of the column by inlets 24, 24a continuously, and valve 41 controls the discharge from the bottom. Half the column extends above the sea level 30, and baffles 18 are spaced along its whole height. A system of risers 52 allows oil to rise from each zone 34 to the corresponding zone of the similarly inclined baffle above. Rises from the upper two zones communicate via duct 56 with oil collection vessel 38. Valve 41 is pneumatically operated and controlled by means 42 which closes the valve when the liquid level in the column falls to 70 and opens it when the level rises to 68. The intervening space accommodates the liquid inflow during settling periods. The quick-shutting action of the valve produces a hydraulic shock in column 12 which assists separation of oil globules. Vessel 38 is intermittently emptied by a pneumatically actuated and controlled pump 39 in response to the oil level varying between 64 and 66. Main inlet 24 delivers water from a first settling tank which handles the well output. Secondary inlet 24a delivers contaminated rain water etc, via a filter 80. The column 12 is supported on the sea bed at 16 and/or by clamps 17 from the main well structure. Discharge water may be sampled by pipe 104. Fig. 5 (not shown) illustrates the shape and mounting of a baffle 18. Baffles are inclined at 25-65 degrees and spaced apart (b in Fig. 4B) by ¢ inch to 10 feet. Figs. 4A, B (not shown) illustrates how column 12 is built up of sections. Fig. 4B also illustrates how zones 34 may be divided by upright plates 97b. Fig. 7 (not shown) illustrates an alternative discharge valve 41 in a protecting housing. In Figs. 8-10 (not shown), which is for use in deeper water than the Fig. 1 model, most of the column is submerged, the bottom of the column is open to the sea and pipes (154, 156) deliver the water to a location where the baffles 18 begin below the sea level. Intermittent flow is achieved by a valve upstream of the column and downstream of a buffer-tank (165). The upper end of the column acts as an oil-storage zone and encloses an oil-discharge pump (157) which is switched on and off as the oil-water interface falls below (164) and rises above (162). Air-lift devices (Figs. 9, 10) enable discharge water to be sampled from the bottom of the column. A device (168) stops well production if the level in column 12 rises too far.