MXPA02003562A

MXPA02003562A - Treating a formation using a foam forming composition.

Info

Publication number: MXPA02003562A
Application number: MXPA02003562A
Authority: MX
Inventors: Jozef Maria Van Eijde Gerbrand
Original assignee: Shell Int Research
Priority date: 1999-10-14
Filing date: 2000-10-12
Publication date: 2002-10-23
Also published as: EA003955B1; AU768666B2; NZ517932A; GB2372525B; NO20021735D0; OA12064A; AU1137601A; GB2372525A; EA200200444A1; GB0207248D0; WO2001027218A1; NO20021735L

Abstract

A method of treating a formation around a wellbore extending from a hydrocarbon bearing zone comprising the steps of interrupting production from the hydrocarbon bearing zone; introducing into the hydrocarbon bearing zone a foam forming composition comprising a surfactant in oil solution; and resuming production from the hydrocarbon bearing zone.

Description

TREATMENT OF A FORMATION USING A FOAM FORMING COMPOSITION Description of the Invention The present invention relates to the production of crude oil from an underground zone containing hydrocarbons, wherein the crude oil is produced through a well borehole that extends from the area containing hydrocarbons to a manhole. well on the surface. At present, the phrase "extending from the area containing hydrocarbons" is intended to cover also the extension through the area containing hydrocarbons, which is a well borehole that, at least in most of the its length is lined with a tubing, where the tubing may be absent in the area containing hydrocarbons, or where the tubing may extend along the entire length of the pithole. to make perforations in the tubing to allow production, in the specification and in the claims the word "• oil" will be used to refer to crude oil.

In many areas that contain hydrocarbons, there is not only oil present, but also an associated natural gas.

It will be understood that this associated natural gas is produced together with the oil. On the surface, this gas has to be REF. : 137006 separated from oil. Since it is not always possible to use natural gas, it has to be inflamed. It is known that, over time, the amount of natural gas that is produced with the oil increases, and more gas will have to be ignited. It is an object of the present invention to treat the formation around the borehole to reduce the amount of gas produced with the oil. For this purpose the method for treating a formation around a well borehole extending from an area containing hydrocarbons comprises the steps of: stopping production from the area containing hydrocarbons; introducing to the hydrocarbon-containing zone a foam-forming composition comprising a solution of surfactant in oil; and resume production from the area containing hydrocarbons. In the method according to the present invention, the gas and the foam-forming composition will create a foam and maintain the foam. This foam will reduce the permeability of the gas. Therefore, in those parts of the zone containing hydrocarbons where the permeability of the gas is initially high, the foam will reduce it. And in the parts of the area where oil is produced, the foam can not be formed. An advantage of the present invention is that the foam-forming composition does not contain water, because the water would increase the water saturation of the formation, which would have an adverse effect on the initial production of oil. An additional advantage is that, since the foam-forming composition does not contain gas, the pumping effort is low. In the method of the invention, the oil used in the foam-forming composition can be any hydrocarbon oil; however, the crude oil that is produced is conveniently used. The concentration of surfactant in the solution is conveniently between 0.5 and 5 volume percent. The surfactant used is conveniently a polymeric compound having good solubility in oil, but low solubility in water (eg, less than 1% by weight, preferably less than 0.1% by weight) or preferably none (less than 0.01% by weight) . Conveniently, the molecular weight of the surfactant varies in the range of 5,000 to 20,000. Nonionic surfactants are preferred. For example, suitable surfactants include polyesters prepared from acrylates, methacrylates and other vinyl ethers, or siloxanes. Examples of the first class of surfactants include fluoroaliphatic polyesters containing fluoroacrylate derivatives, such as FLUORAD FC-740 (trademark of 3M Industrial Chemical Products) or similar products from, for example, ATOFINA. Polymethyloctadecylsiloxane, sold by United Chemical Technologies as PS130, is an example of a suitable surfactant based on siloxane. The invention will now be described by way of example in more detail with reference to a laboratory experiment. In the experiment a core sample (model for the hydrocarbon-containing formation) having a diameter of 2.54 cm and a length of 50 cm, and an absolute permeability of 2.3 Darcy (corresponds to 2.3 x 10"8 cm2) was used. The core sample was placed in a cell in order to perform core flood experiments at a pressure of 117.26 kg / cm2 (115 bar) (absolute) .The core sample was first flooded with water, in order to To measure the absolute permeability, the core sample was then flooded with a light crude oil to obtain a core sample with a saturation of formation water filled with the crude oil In all the experiments, nitrogen was used to "simulate the hydrocarbon. In a first experiment (not according to the invention) the oil was displaced by nitrogen, where the core sample was maintained at a temperature of 63 ° C. After injecting, under the conditions of the experiment, a volume of nitrogen equal to 800 pore volumes, the relative gas permeability measured from the core sample was 0.27. The relative permeability is the ratio of the measured permeability to absolute permeability. In a second experiment (according to the invention), the oil was replaced by an oil containing 1 volume percent FLUORAD FC-740. And the oil was displaced by nitrogen at a temperature of 63 ° C. The nitrogen now caused the formation of a foam and the relative gas permeability after injecting, under the conditions of the experiment, a volume of nitrogen equal to 800 pore volumes was 0.02. This is a considerable reduction in gas permeability. In addition, it was found that most of the mobile oil was displaced after injecting the first pore volumes of nitrogen, which can be expected due to the mobility of the strongly reduced gas. After having injected approximately 800 volumes of nitrogen pore, the core sample was filled with foam formed by the injection of nitrogen. In order to discover if the foam would harm the oil production, an additional experiment was carried out. In this experiment oil without surfactant was injected into the core sample filled with foam. After injecting approximately 7 volumes of oil pore, the relative oil permeability was approximately 1. The experiments are representative for underground conditions where oil is produced from an area containing hydrocarbons in the presence of free gas. From the experiments it can be concluded that the present invention provides a simple method for treating the formation to reduce the permeability of the gas formation and thereby reduce the amount of gas that is produced with the oil. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims

CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A method for treating a formation around a well borehole extending from an area containing hydrocarbons, characterized in that it comprises the steps of: interrupt production from the area containing hydrocarbons; introducing to the hydrocarbon-containing zone a foam-forming composition comprising a solution of surfactant in oil; and resume production from the area containing hydrocarbons.
2. The method according to claim 1, characterized in that the concentration of surfactant in the solution is between 0.5 and 5 volume percent.
3. The method according to claim 1 or 2, characterized in that the surfactant used is a polymeric compound having good solubility in oil, but low solubility in water.
4. The method according to any of claims 1 to 3, characterized in that the surfactant is a non-ionic surfactant.
The method of compliance any of claims 1 to 4, characterized in that the molecular weight of the surfactant varies in the range of 5,000 to 20,000.
The method according to any of claims 1 to 5, characterized in that the surfactant is selected from polyesters prepared from acrylates, methacrylates and other vinyl ethers or siloxanes.
The method according to claim 6, characterized in that the surfactant is a fluoroaliphatic polyester containing fluoroacrylate derivatives.
8. The method according to claim 7, characterized in that the surfactant is FLUORAD FC-740.