JPS61102994A - 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 improves the resistance factor and residual resistance factor of the injection fluid against an oil layer, and further improves oil recovery. This improves the efficiency of drug use.

Conventional Technology Petroleum extraction technology has evolved through three major stages to date. The first stage is called the present-subsequent recovery method, 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 the 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 regions; (2) causes fingering; (3) runs under or over viscous crude oil; and (4) channels through fractures. These factors are said to be the cause of low recovery rates. Therefore, in order to further improve the oil recovery rate, it is considered to increase the flow resistance of the injection water.
It is known to use an aqueous polymer solution as a means for this purpose, and polyacrylamide as a synthetic polymer and xanthan gum as a biopolymer have been put into practical use.

The third stage is the technology to recover this residual oil, and En
Hanced Oil Recovery (EOR)
) is called 4f.

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. This invention has not yet been sufficiently investigated.The present invention involves the addition of a small amount of additives to polyacrylamide (acrylamide-based polymer), thereby achieving even better oil recovery properties. The aim is to provide medicines for patients with disabilities.

Means/Function for Solving the Problems The present invention provides a resistor comprising 100 parts by weight of an acrylamide polymer and 0.05 to 5.0 parts by weight of a thiourea.
9') -H, RU"itc#*ヮ7,7.-. Yaa 54 polymer composition for oil recovery.

That is, the present invention adds a small amount of thioureas to the polyacrylamide aqueous solution conventionally used for forced oil recovery, thereby improving the resistance factor (RF) and residual resistance factor (RRF) that lead to an increase in oil recovery rate.
This improves the oil recovery rate and increases the oil recovery rate, and requires less polyacrylamide than before.

It is known that RF and RRF can be calculated by the following method* (Polymer 5science a
nd Tech-nology Vol, 2. Wat
er-9olub! e Polymers P2O3-
+2t3゜Water-Solable PoX Tew
ets in Petroleum Recov
ery).

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 (M) is defined as follows.

M=(KW/lumu W)/(KO/sire 0) Reference
Reference φ (1) Here, Kw is the relative permeability of water at the saturation rate of immobile oil Ko is the relative permeability of oil at the saturation rate of immobile water Le W is the viscosity of water Le 0 is the viscosity of oil In the case of normal pressurized water M The fact that M has a very high value of lO~30 and that water is 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 Polybou solution, and in order to know the performance of the Polybou solution for lowering M, the resistance factor RF is measured.

RF= (Kw/JLw)/(Kp/LeP)...(2
) Here, KP is the relative permeability of the polymer solution relative to the saturation rate of the fixed oil.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. It is easily understood from equation (1) and its explanation that a large value of is preferable as an oil recovery solution. Another feature of the acrylamide polymer solution is that once the polymer solution is passed through the rock, it semi-permanently reduces the permeability of the rock. The residual resistance factor RRF indicates this decrease in permeability.

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.

In addition, the above equations (2) and (3) are as follows: become.

= (QW/ΔPw) (ΔPp/Qp) = (ΔPp/Q
p)/(ΔPw/Qw)---(4)RRF= (Q
w/ΔPw)(ΔPw'/Qw')=(ΔP'w/QW
')/(ΔPw/Qw) @ *(5) The inventor has these 2
The composition of the oil recovery polymer composition of the present invention is limited to a specific range based on two resistance factors, and the amount of thioureas added is less than 0.05 parts by weight per 100 parts by weight of the acrylamide polymer. If so, the effect of increasing the two resistance factors mentioned above cannot be expected, and if the amount of thioureas added exceeds 5.0 parts by weight, the two resistance factors mentioned above will decrease on the contrary. That is, the two resistance factors have maximum values between 0.05 and 5.0 parts by weight of thioureas per 100 parts by weight of the acrylamide polymer; Preferably it is 0.5 to 2.0 parts by weight.

In addition, 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), or,
Polymers containing methacrylamide, acrylonitrile, dimethylaminoethyl methacrylate tertiary salts, quaternized products, lower alkyl acrylic esters, etc., to the extent that water solubility is not impaired, or so-called copolymerization reactions of these 7-ionic polymers. The present invention is not limited to those based on the above, 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.

Also, the apparent degree of polymerization is preferably 10,000 or more, 1.%.
.

In addition, the thioureas referred to in the present invention refer to the following general formula (wherein Rt and R2 are hydrogen or an organic group mainly composed of carbon and hydrogen, and R3 is an organic group mainly composed of carbon and hydrogen). It is a compound having at least one structural moiety represented by the following.

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

In addition, the polymer composition of the present invention is not only a solid composition in which an acrylamide polymer and a thiourea are mixed in solid form, but also a solid composition in which the acrylamide polymer and a thiourea coexist in a state of use. This includes cases where they coexist in solution or slurry form, gel form and powder form, etc., and the method for mixing acrylamide polymers and thioureas is generally known. Either method can be used.

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 100 PP11 to 10,000 ppm aqueous solution.
A concentration of is preferred.

Example acrylamide 80 mol%, sodium acrylate 20
A copolymer consisting of mol%, its molecular weight is approximately 15.00
0.000 of an acrylamide polymer was mixed with 0.000 of common salt.
Using salt water (solvent) containing 14 g/u and 0.18 g/u of calcium chloride anhydride, the concentration of acrylamide polymer in the solution was adjusted to 300 ppm, and a predetermined amount of powdered thiourea was added and dissolved with stirring. Seven samples having different thiourea contents shown in Table 1 were obtained.

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 Seat pressure l Solvent Qw ΔPw2 Sample Qp
ΔPp3 Solvent QL, ΔP
'wRF= (ΔPp/Qp)/(ΔPw/Qw) @
--(4) RRF= (ΔP'W/QW')/(ΔPw
/Qw) - (5) The obtained results are shown in Table 1.

As can be seen from the autopsy results in Table 1, the resistance factor and residual resistance factor reach their maximum peaks when the amount of thiourea added is 0.05 to 5.0% by weight, which increases the oil recovery rate as mentioned above. It is.

Effects of the Invention According to the polymer composition for oil recovery of the present invention, it is possible to reduce the amount of polyacrylamide used conventionally in polymer flooding methods or to improve the oil recovery rate, and the economic effect thereof is extremely high. big.

Claims (1)

[Claims] 100 parts by weight of acrylamide polymer and 0.0 parts by weight of thioureas.
A polymer composition for oil recovery with improved resistance factor and residual resistance factor comprising 0.05 to 5.0 parts by weight.