Di-Alkyl Chain Surfactants as a Main Surfactant for Enhancing Oil Recovery for Tight Oil Formations

Some reservoirs have tight oil formations, such as the Changqing reservoir. The surfactant polymer flooding and low-tension gas flooding are two potential chemical flooding methods for use in tight oil formations. In these methods, an oil displacement agent, or surfactant, is added. Derivatives of nonionic surfactants with extended chains (by propylene oxide and ethylene oxide) from di-alkyl alcohols were developed and tested. A synergistic blend of surfactants was developed between the di-alkyl chain surfactants and a commercially available anionic surfactants that lowers interfacial tension and improves surfactant solubility in high salinity water and oil.

FIELD

The disclosure relates generally to oil recovery. The disclosure relates specifically to surfactants used in oil recovery.

BACKGROUND

Enhanced oil recovery is the process of increasing the amount of oil that can be recovered from a reservoir. The Changqing reservoirs in China have tight oil formations. Tight oil is oil trapped in rock formations such as shale, limestone, or tight sandstone. These rock formations have lower permeability than other reservoirs. Often, hydraulic fracturing is utilized to create adequate permeability in order to access the oil economically.

It would be advantageous to have an oil displacement agent to use in enhanced oil recovery. Moreover, it would be advantageous to have a surfactant to act as an oil displacement agent to improve oil recovery for the Changqing tight oil reservoir.

SUMMARY

A first embodiment of the present technology provides for a method of making a di-alkyl chain surfactant. A nonionic surfactant can first be produced by reacting a di-alkyl chain primary alcohol with ethylene oxide and propylene oxide. The resultant extended-chain nonionic surfactant can then be reacted with a base, a chloride acid or a salt derivative of a chloride acid, and a glycol ether. Water can be added to the resulting product to produce the di-alkyl surfactant.

The method can further include nitrogen purging during the reaction steps. In some embodiments, a condensation trap or condensation receiver can be used to collect water or organics for reuse.

In some embodiments, the nonionic surfactant can be heated to a temperature of less than 50° C. prior to the reaction with the base.

The base can be any metal hydroxide or metal alkoxide, such as potassium hydroxide, sodium hydroxide, sodium methoxide, sodium ethoxide, potassium methoxide, lithium hydroxide, or potassium tert-butoxide. The base can be added at a ratio of 1-2 moles for every 1 mole of nonionic surfactant. The base can be reacted at about 90-120° C. for about 0.5 to 3 hours with the nonionic surfactant.

The chloride acid can be a monochloroacetic acid, or its salt derivative such as sodium monochloroacetate (SMCA). Altematively, the chloride acid can be a 3-chloro-2-hydroxy-1-propanesulfonic acid (CHPS) or its salt derivatives such as 3-chloro-2-hydroxy-1-propanesulfonic acid sodium salt. The chloride acid can also be chlorosulfonic acid. The chloride acid or its salt derivative can be added at a ratio of 1-1.9 moles for every 1 mole of the nonionic surfactant. The chloride acid can be reacted at below 100° C. and above 70° C. for about 2-5 hours. The chloride acid can further be reacted until the free chloride ion within the reaction is in the range of about 1.2-2.7%.

In some embodiments, the glycol ether can be a tetrapropylene glycol monomethyl ether, a tripropylene glycol monomethyl ether, a tripropylene glycol monoethyl ether, a tripropylene glycol dimethyl ether, a tripropylene glycol diethyl ether, a dipropylene glycol dimethyl ether, a dipropylene glycol diethyl ether, a dipropylene glycol monomethyl ether, or a diethylene glycol monobutyl ether. The glycol ether can be added at a 0.5 to 2 mass ratio with the nonionic surfactant. The glycol ether can be reacted for about 1-3 hours at about 50 to 90° C. with the preceding portions of the reaction. Water can be added at a 0.5 to 2 mass ratio with the nonionic surfactant to produce the final product of the di-alkyl surfactants.

In some embodiments, the di-alkyl surfactant can form Type III microemulsions with aqueous phase and oil phase. These microemulsions can have interfacial tensions of less than 10-3mN/m. In some embodiments, the type III microemulsions can be formed in aqueous fluid with 30.000 to 120.000 ppm of total dissolved solids. In some embodiments, the di-alkyl surfactant produced by the reaction can be a clear, viscous liquid.

DETAILED DESCRIPTION

The particulars shown herein are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present disclosure only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of various embodiments of the disclosure. In this regard, no attempt is made to show structural details of the disclosure in more detail than is necessary for the fundamental understanding of the disclosure, the description taken with the drawings making apparent to those skilled in the art how the several forms of the disclosure may be embodied in practice.

Surfactant-polymer (SP) flooding and low-tension gas (LTG) flooding are proposed as two chemical flooding methods for enhanced oil recovery for the Changqing tight oil formation reservoir. In both methods, the key additive is the oil displacement agent or surfactant. Initially, a series alkyl propoxy sulfates (APS) (primary surfactant) with alkyl benzyl sulfonates (ABS) (co-surfactant) were tested. Following those tests, di-alkyl chain surfactants as the main surfactant will be used to run chemical flooding tests to demonstrate the efficiency of the enhance oil recovery.

Synergistic blends of surfactants using di-alkyl surfactants as the main component with the help of co-surfactant of ABS were developed those lower interfacial tension (IFT) and improve surfactant solubility in high salinity water and oil.

A first embodiment of the present technology provides for a method of manufacturing an oil displacement agent. The oil displacement agent can be used to improve oil recovery in tight oil reservoirs. The tight oil reservoirs can have a high salinity and a high temperature.

The oil displacement agent can be manufactured from a reaction of a di-alkyl primary alcohol. The di-alkyl primary alcohol can be, but is not limited to, any Guerbet alcohol. The di-alkyl primary alcohol can further be reacted with EO and PO to form the initial nonionic surfactant. In some embodiments, there can be between 0-30 EO and between 0-50 PO as a part of the nonionic surfactant.

The resulting nonionic surfactant can have a formula of CmH2m+1CH(CnH2n+1)CH2O(PO)x(EO)yH. In the formulation, m can be 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 or any combination thereof; n can be 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or any combination thereof; m+n can be 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, or any combination thereof; x can be between 0-50; and y can be between 0-30. The nonionic surfactant can then be heated to a temperature of less than 50° C. During this time the nonionic surfactant can also be nitrogen purged.

At this time, a base can be added to the nonionic surfactant. The base used can include, but is not limited to, potassium hydroxide (KOH), sodium hydroxide (NaOH), sodium methoxide (MeONa), sodium ethoxide (EtONa), potassium methoxide (MeOK), lithium hydroxide (LiOH), potassium tert-butoxide (t-Bu-OK), and other metal hydroxide or metal alkoxide bases. When using KOH, the KOH can be added at a ratio of 1-2 moles for every 1 mole of the nonionic surfactant. During this reaction, the temperature can be maintained at between 90 and 120 degrees for about 0.5 to 3 hours. The nitrogen purge and/or vacuum can be maintained during this time. A condensation trap or receiver can be used to collect all water formed, maximized at a 1 to 1 mole ratio of nonionic surfactant.

After the reaction is complete, the resulting product can be cooled to about 75-95° C. for the addition of a chloride acid or its derivative. At this time, a sodium monochloroacetate (SMCA) can be added to the system. The SMCA can be added at a ratio of 1-1.9 moles for every 1 mole of the nonionic surfactant. The reaction can be maintained at a temperature below 100° C. for about 2-5 hours. The reaction can be allowed to continue until the free chloride ion of the composition is in the range of 1.2-2.7%. The nitrogen purge can be maintained during this time.

Alternatively, monochloroacetic acid, chlorosulfonic acid, 3-chloro-2-hydroxy-1-propanesulfonic acid or their sodium salts, such as 3-chloro-2-hydroxy-1-propanesulfonic acid sodium salt (CHPS) can be added instead of SMCA. When using CHPS, the reaction can proceed similar to SMCA.

Following this reaction, tetrapropylene glycol monomethyl ether, tripropylene glycol monomethyl ether (TPM), a tripropylene glycol monoethyl ether, a tripropylene glycol dimethyl ether, a tripropylene glycol diethyl ether, a dipropylene glycol dimethyl ether, a dipropylene glycol diethyl ether, a dipropylene glycol monomethyl ether, or a diethylene glycol monobutyl ether can be added to the reaction. The TPM can be added to the system at a 0.5 to 2 mass ratio with the nonionic surfactant. The reaction can be continued for about 1-3 hours. This can continue until all of the organic chlorides from the SMCA or the CHPS are free chloride ions. The nitrogen purge can be maintained during this time. A condensation trap or receiver can be used to collect all evaporated organic chemicals for recycle or reusage.

Finally, water can be added to the formulation to arrive at the final surfactant. The water can be added at a 0.5 to 2 mass ratio with the nonionic surfactant. The resulting surfactant can be a clear, viscous liquid.

FIG.1is a salinity scan for microemulsion phase behavior tests at 200° F. using dodecane as the oil phase. Phase behavior tests can be used to show the formation of Type III microemulsions. A microemulsion is a thermodynamically stable fluid. Microemulsions can be classified as Winsor Type I, Type II or Type III. Type III microemulsion is a three-phase mixture with an excess brine phase, an excess oil phase, and a microemulsion phase. Typically, a lower interfacial tension of surfactants means a higher volume of the microemulsion phase. These Type III microemulsions inFIG.1have low interfacial tensions of less than 10-3mN/m. In addition, the Type III microemulsions can be formed in salinity ranges of between about 30.000 ppm to about 120.000 ppm of total dissolved solids, which outperforms a lot of commercially available surfactant formula.

FIG.2is a salinity scan for microemulsion phase behavior tests at 200° F. using crude oil as the oil phase. The crude oil is from an oil field of interest. Comparing withFIG.1, we know that this surfactant formula performs well for the field crude oil.