Wells – Processes – Separating material entering well
Patent
1996-03-26
1999-01-19
Dang, Hoang C.
Wells
Processes
Separating material entering well
166243, 2105122, E21B 4338
Patent
active
058604766
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method of recovering hydrocarbons in a sub-surface reservoir, wherein a production flow is subjected to a separation process in the well hole.
BACKGROUND OF THE INVENTION
To separate oil and water in a well hole is known, for example, from U.S. Pat. No. 4,296,810. The separator used is built up of semi-permeable membranes. The separated water, produced water, is injected into a waste zone above or below the production zone.
U.S. Pat. No. 4,659,343 makes known the separation of carbon dioxide from light hydrocarbons with the aid of a membrane arrangement. During the separation through the semipermeable membrane, a condensate emerges (hydrocarbons in liquid form) in contact with the membrane. These (liquified) liquid hydrocarbons are separated from the gases which do not pass through the membrane. This separation takes place by means of conventional membrane technology used in traditional processes within the processing industry.
Gravitation separation of hydrocarbons and water in a well hole is known, for example, from U.S. Pat. No. 4,766,957. The produced water flows into a waste zone and the oil passes upward to the surface.
U.S. Pat. No. 4,805,697 describes the reinjection of produced water, resulting from the separation of hydrocarbons and water in a centrifugal separator, of the dynamic or static type, regulated as a function of the hydrocarbon content in the produced water.
Hollow fiber separation (the hollow fibers are of a semipermeable membrane material) is discussed in U.S. Pat. No. 5,176,725.
NO B 173426 describes the use of cyclone separators in the separation of oil and water in a well hole.
The processing of a production flow in a well hole gives rise to great advantages, especially by virtue of the fact that one does not need to lift, separate or remove the produced water.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide, in the hole, a process which makes possible the supply of gas free of unwanted gases at the surface, with the possibility of reinjecting produced water and the separated, unwanted gases into a waste zone, so that one avoids cost-intensive lifting etc, of the unwanted parts of the production flow and avoids having to conduct these unwanted parts back into the reservoir through special reinjection/waste wells or dumping into the sea or the atmosphere.
According to the invention, it is proposed to carry out a cyclone separation of gas and liquid with a subsequent cyclone separation of condensate/oil from water at high pressure in the well hole, as well as a separation of the gas phase's unwanted gases, H.sub.2 S, CO.sub.2 and H.sub.2 O, by using membranes under high pressure in the well hole.
The separated gases may to advantage be dissolved in a liquid, preferably sea water, prior to reinjection into a waste zone, a reinjection zone or to a recipient.
Such highly pressurised sea water in a well/reservoir can dissolve large quantities of gas. The reject from the membrane may therefore contain small amounts of gas together with H.sub.2 S, CO.sub.2, which it is not economical to separate further and which again may be dissolved in sea water through a chamber which mixes gas and sea water and dissolves the residual gases for further injection into a waste reservoir or for further dilution and emission to a recipient.
The invention relates also to an arrangement for use for recovering hydrocarbons in a sub-surface reservoir, comprising cyclone separators inside a well hole. The arrangement is characterised in that it comprises a cyclone separator for separating gas and liquid and a cyclone separator for separating condensate/oil from water at high pressure in a well hole, and a membrane arrangement for the separation of the gas phase's unwanted gases, H.sub.2 S, CO.sub.2 and H.sub.2 O, at high pressure in a well hole. The cyclone separators and the membrane arrangement may advantageously be placed in a pipe string, which may be a permanent part of a production string or a free-standing part which
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Anil A/S
Dang Hoang C.
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