JPS61102995A - Polymer composition for recovering petroleum - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an injection fluid used in forced oil recovery (EOR), and is a polymer composition for oil recovery that improves oil recovery with a small amount of use. Regarding.

Conventional Technology Petroleum extraction technology has evolved through three major stages to date. The first stage is called the current-next agreement, in which oil is recovered as it self-gushes using the natural energy of the oil layer, and the recovery rate is said to be at a local level of reserves. The second stage is called the secondary recovery method, in which water or gas is artificially injected from the ground into oil fields where the artesian ability has diminished to push out the oil.

Depending on these recovery methods, oil that exists as oil droplets in the pores of reservoir rocks, oil that adheres to the rock surface as an oil film, and oil that exists in areas that do not come into contact with gas or water in secondary recovery methods may be untreated. It is believed that up to 50% of the crude oil remains underground after recovery.

In the secondary recovery method using pressurized water or pressurized gas (1
) the injected fluid avoids low permeability layers or low permeability zones, (2) causes fingering, (3) runs under or through soil with high viscosity, (channeling through zero cracks, etc.) is said to be the cause of low recovery rates.In order to further improve the oil recovery rate, it is considered to increase the flow resistance of the injection water, and it is known that an aqueous polymer solution is used as a means for this purpose. , polyacrylamide as a synthetic polymer, and xanthan gum as a biopolymer are in practical use.

The technology to recover this residual oil is the third step,
anced Oil Recovery (EOR)
It is called.

The present invention relates to an EOR method.

Problems to be Solved by the Invention As mentioned above, it is already known that polyacrylamide can be used to increase the flow resistance of injection fluid, but the modification of the acrylamide polymer itself has not yet been sufficiently investigated. The present invention aims to provide an oil recovery agent that exhibits even better injection fluid properties by adding a small amount of additives to an acrylamide polymer.

Means/Function for Solving the Problems The composition of the present invention is as follows: 1. 100 parts by weight of an acrylamide polymer;
・Mercaptobenzimidazole or its salt ・0.5
100 parts by weight of an acrylamide polymer, 0.5 to 2 parts by weight of 2-mercaptobenzimidazole or a salt thereof; .0
This is a polymer composition for oil recovery with improved resistance factor and residual factor, which comprises 0.05 to 5.0 parts by weight of a thiourea.

Next, the composition of the oil recovery polymer composition of the present invention will be explained in more detail.

In the aforementioned oil recovery method using pressurized water, it has been known for a long time that the mobility ratio between the displacement fluid, ie, pressurized water, and the fluid to be replaced, ie, crude oil, greatly influences the recovery rate.

The mobility ratio CM) is defined as follows.

M= (Kw/Tile W) / (0 for K oZ)・Skewer・C
1) Here, Kw is the relative permeability of water at the immobile water saturation rate KO is the relative permeability of the sleeve at the immobile water saturation rate W is the viscosity of water JLo is the viscosity of oil For normal pressurized water M is lθ ~ 30 The fact that water exhibits a property of being more mobile than oil is associated with a low oil recovery rate.
If the temperature is lowered to 100%, the action of pushing out the oil will be carried out smoothly.

In the polymer attack method, the above-mentioned water is replaced with a polymer solution, and in order to know the performance of the polymer solution for reducing M, the resistance factor RF is measured.

RF= (Kw/pw)/(Kp/pp) No.・(2
) Here, Kp is the relative permeability of the polymer solution at the immobile water saturation rate. P is the viscosity of the polymer solution. This RF is influenced by the concentration of the polymer, the molecular weight of the polymer, the properties of the solvent, etc., but the value of this RF is It is easily understood from equation (1) and its explanation that the larger the value, the better the solution for oil recovery.

Next, another feature of the acrylamide polymer solution is that
By passing a polymer solution through a rock, the permeability of the rock is semi-permanently reduced. The factor that indicates this decrease in penetration rate is the residual resistance factor R.
It is RF.

As this RRF increases, the permeability of the rock after passing through the polymer solution decreases, which is, in principle, preferable for the polymer exploration method in which crude oil is mined by pushing the crude oil layer with the polymer solution layer, and pushing the polymer solution layer with the water layer. It is a phenomenon.

Note that the above equations (2) and (3) are as follows: QL A・ΔP However, since A: cross-sectional area of the core L: core length Q: flow rate, the following equations (4) and (5) are obtained. become that way.

= (QW/ΔPw) (ΔPp/Qp) = (ΔPp/Q
p)/(ΔP W/QW) −e 6 (4) RRF=
(Qw/ΔPw) (ΔPw'/Qw')=(ΔP'
w/Qw')/(ΔPw/Qw) (5) The inventor limited the composition of the oil recovery polymer composition of the present invention to a specific range based on these two resistance factors,
If the amount of 2-mercaptobenzimidazole (sometimes abbreviated as 1'lBI) or its salt added to 100 parts by weight of the acrylamide polymer is less than MBI & 0.5 parts by weight, the above two resistances will be met. No effect of increasing the factor can be expected, and the amount of MBI or its salt added may be lower than MHI.
If it exceeds 2.0% by weight, the above two resistors 71''- will actually become weaker than KTt6.tfZh%2
Q(7)l! ;) *7y9ter has a maximum value within the above-mentioned limited range.

Furthermore, 0.05 parts of NBI or a salt thereof is added to the composition within the above range, based on 100 parts of the acrylamide polymer.
By adding thioureas in the range of 5.0 parts by weight to 5.0 parts by weight, the above-mentioned two resistance factors are further increased, but addition of thioureas outside these ranges actually decreases the two resistance factors.

Note that in the present invention, the acrylamide polymer is
Includes all water-soluble polymers containing an acrylamide component.

Specifically, copolymers of acrylamide and acrylic acid (salt), methacrylic acid (salt), 2-acrylamide-2-methylpropanesulfonic acid (salt), etc., or water-soluble in these 7-ionic polymers A polymer containing methacrylamide, 7-crylonitrile, dimethylaminoethyl methacrylate tertiary salt, quaternized product, lower alkyl acrylic acid ester, etc. within a range that does not impair properties.

Furthermore, it is not limited to those based on so-called copolymerization reactions, but also includes those in which an amide group is converted into another functional group by chemical reactions in and out of polymerization, such as those in which an amide group is hydrolyzed with an alkali or converted into a methylol group.

It also includes mixtures of two or more of the above polymers.

Further, the apparent degree of polymerization is preferably 10,000 or more.

Next, 2-mercaptobenzimidazole or a salt thereof is a water-soluble compound represented by the following general formula.

(However, X represents hydrogen, an alkali metal, or ammonium.) When X is hydrogen, it has poor solubility, so it is usually used in the form of sodium salt, potassium salt, or ammonium salt.

In addition, the thioureas referred to in the present invention are represented by the following general formula (% formula % (%) represents an organic group consisting of carbon and hydrogen, and R3 represents an organic group mainly consisting of carbon and hydrogen). A compound having at least one structural moiety.

For example, such thioureas include thiourea,
N,N''-diphenylthiourea, diortho-tolylthiourea, ethyleneurea, and the like.

Furthermore, the polymer composition of the present invention is not limited to the case where the acrylamide-based polymer, MHI or its boundary, 8, and thioureas are mixed to form a solid state, but also when the above three components substantially coexist in the state of use. For example, it may be in the form of a solution, slurry, gel, etc. As for the method of mixing these champions, any commonly known method can be employed.

Therefore, the concentration at which the polymer composition of the present invention is effective for oil recovery is about 1100 ppm to 50,000 ppm aqueous solution, particularly 1ooppa+ to to, ooopp
The preferred concentration is I9 - Example acrylamide 80 mol%, sodium acrylate 20
A polymer consisting of mol%, whose molecular weight is approximately 15,000
,000 of an acrylamide-based polymer, salt Q, 1
Using salt water (solvent) containing 4g/i and 0.18g/n of calcium chloride anhydride, the concentration of acrylamide polymer in the solution was 3009P! )IBI
, 1,000 urea was added in a predetermined amount and dissolved with stirring to obtain samples having different compositions as shown in Table 1.

A core test was conducted on these polymer composition solution samples using Berea sandstone with a permeability of 900 to 1000 millidarcy as a model of oil reservoir rock.

For each sample, flow the fluid into a new core in the following order, find the flow rate Q and the pressure difference ΔP before and after the core, and use equations (4) and (5)
The resistance factor RF and the residual resistance factor RRF were determined using the formula.

Note that the liquid temperature was maintained at 25°C±1°C.

Measurement order Fluid Flow rate Differential pressure 1 Solvent Qw Δpw2 Sample Qp
ΔPp3 13 medium Q'W Δp
'wRF= (ΔPp/Qp), /(ΔPw/Qw)・
...(4) RRF= (ΔP'W/QW')/(ΔPW
/QW)...(5) The results obtained are shown in Table 1.

Part by weight added to 100 parts by weight of the present acrylamide polymer Effect of the invention According to the polymer composition for oil recovery of the present invention, the amount of polyacrylamide used conventionally used in the polymer attack method can be reduced or the oil recovery rate can be improved. The economic effect is extremely large.

Claims (1)

[Scope of Claims] 1. An oil recovery polymer with improved resistance factor and residual resistance factor, comprising 100 parts by weight of an acrylamide polymer and 0.5 to 2 parts by weight of 2-mercaptobenzimidazole or its salt. Composition. 2. Resistance factor and residual factor consisting of 100 parts by weight of acrylamide polymer, 0.5 to 2.0 parts by weight of 2-mercaptobenzimidazole or its salt, and 0.05 to 5.0 parts by weight of thioureas. Improved oil recovery polymer compositions.