A multi-point sterilization method for inhibiting viscosity loss of oilfield ASP polymer

Abstract

The present disclosure relates to a multi-point sterilization method for inhibiting the viscosity loss of oilfield ASP polymer, which adds the sterilization agent according to different stages of the ASP, wherein the sterilization agent adding point is arranged on the external delivery pipeline of the sewage station in the blank water flooding stage and the subsequent water flooding stage; the sterilization agent adding point is arranged at the inlet of the water injection pump of the water injection station in the pre-polymer slug stage and the subsequent polymer protection slug stage; the sterilization agent adding point is arranged on the low-pressure binary pipeline of the binary deployment station in the ASP main slug stage and the ASP auxiliary slug stage; after the application of the present application, the viscosity loss of the three-component system is controlled within the 20% index range, which has a wide application prospect for reducing the cost and increasing the efficiency of the ASP, and provides important support for ensuring the development effect of the original system of the ASP.

Description

Technical Field

[0001] This disclosure relates to the field of water injection and distribution technology for oilfield surface engineering water treatment, specifically to the sterilization process for the preparation and dilution water of ternary composite flooding, and particularly to a multi-point sterilization method for inhibiting the viscosity loss of polymers in oilfield ternary composite flooding. Background Technology

[0002] Currently, oilfields commonly employ a combined physical and chemical sterilization process at wastewater treatment plants to centrally treat bacteria in exported water. This involves installing physical sterilization devices and adding bactericides before the export tanks at the wastewater treatment plant. However, during application, it has been found that bacteria can re-grow due to the long distances of the wastewater export pipelines. Furthermore, when using ternary composite flooding produced water to prepare the original system for displacement, the alkylbenzene sulfonates and other surfactants in the dilution water contain n-butanol, which easily acts as a nutrient for bacteria, accelerating bacterial reproduction. The original process cannot achieve sterilization at this stage. Therefore, current sterilization methods cannot guarantee the viscosity requirements of the ternary composite flooding injection system, thus affecting development results.

[0003] In recent years, researchers in related fields have proposed several methods for disinfecting oilfield wastewater to inhibit bacterial content. For example, CN111662700B discloses a method for reducing viscosity loss by regulating the microbial community structure in polymers formulated with oilfield produced water. CN111662701A discloses an eco-friendly viscosity stabilizer suitable for oilfield polymer-driven processes and its application method. Both of these methods have developed novel agents, but neither considers the effect of the dosing method on inhibiting bacterial content in wastewater and reducing polymer viscosity loss.

[0004] The development process of ternary composite flooding is divided into six different stages: blank water flooding, pre-polymer protection slug, ternary main slug, ternary secondary slug, subsequent polymer protection slug, and subsequent water flooding. The existing dosing method is that the bactericide dosing point is set at the wastewater treatment plant regardless of the stage. Summary of the Invention

[0005] In view of this, this disclosure provides a multi-point sterilization method to suppress polymer viscosity loss in ternary composite flooding in oilfields, which solves the problem that existing bactericide dosing methods do not take into account the characteristics of bacteria at different stages of ternary composite flooding development, resulting in the need to increase the amount of bactericide added to control polymer viscosity loss.

[0006] To achieve the above-mentioned objective, the multi-point sterilization method for suppressing viscosity loss of ternary composite flooding polymers in oilfields includes:

[0007] In the blank water drive stage and subsequent water drive stage of the ternary composite flooding, the bactericide dosing point is located on the sewage treatment plant's external pipeline; in the pre-polymer slug stage and subsequent polymer protection slug stage, the bactericide dosing point is located at the inlet of the water injection pump of the water injection station; in the ternary main slug stage and ternary auxiliary slug stage, the bactericide dosing point is located on the low-pressure unary pipeline of the binary mixing station.

[0008] In this disclosure and possible embodiments, in the pre-polymer slug stage and the subsequent polymer protection slug stage, a method of injecting polymer prepared with clean water combined with polymer diluted with wastewater is adopted.

[0009] In the present disclosure and possible embodiments, in the ternary main slug stage and the ternary secondary slug stage, an injection method is adopted in which ternary produced wastewater is used to prepare polymers in combination with ternary produced wastewater to dilute the ternary composite flooding system.

[0010] In this disclosure and possible embodiments, in the blank water drive stage and the subsequent water drive stage, a sterilization method combining a sterilization device and a sterilizing agent is adopted. The sterilization device adopts an ultraviolet sterilization process, and the sterilizing agent adopts a high-concentration preservative sterilizing agent.

[0011] In this disclosure and possible embodiments, the high-concentration preservative and bactericide is an organic bromine compound bactericide.

[0012] In this disclosure and possible embodiments, an organic bromine compound bactericide is used in the pre-polymer slug stage and the subsequent polymer protection slug stage.

[0013] In this disclosure and possible embodiments, organic bromine compound bactericides are used in the ternary main septum stage and the ternary secondary septum stage.

[0014] In this disclosure and possible embodiments, the bactericide is added via a skid-mounted dosing device.

[0015] The beneficial effects of this invention are:

[0016] The multi-point sterilization method for suppressing polymer viscosity loss in ternary composite flooding provided in this disclosure involves adding the bactericide at different stages of the ternary composite flooding process. In the blank water flooding stage and subsequent water flooding stages, the bactericide addition point is located on the wastewater treatment plant's external pipeline. In the pre-polymer slug stage and subsequent polymer protection slug stage, the bactericide addition point is located at the inlet of the water injection pump at the water injection station. In the ternary main slug stage and ternary auxiliary slug stage, the bactericide addition point is located on the low-pressure unary pipeline at the binary blending station. After applying the technology of this application, the viscosity loss of the ternary recovery system is controlled within the 20% target range. This method has broad application prospects for cost reduction and efficiency improvement in ternary composite flooding and provides important support for ensuring development effectiveness in the formulation of the original ternary composite flooding system. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the specification, serve to illustrate the technical solutions of this disclosure.

[0018] Figure 1 This is a schematic diagram of the location of the bactericide dosing point in the multi-point bactericidal method for suppressing the viscosity loss of ternary composite flooding polymers in oilfields, according to an embodiment of this disclosure;

[0019] In the diagram: 1-Sewage treatment plant, 2-Water injection plant, 3-Dual mixing plant, 4-Preparation plant, 5-Ternary injection plant;

[0020] Figure 2 It is the viscosity curve of the indoor research results. Detailed Implementation

[0021] Various exemplary embodiments, features, and aspects of this disclosure will now be described in detail with reference to the accompanying drawings, in which the specific term “exemplary” means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0022] Furthermore, to better illustrate this disclosure, numerous specific details are set forth in the following detailed description. Those skilled in the art will understand that this disclosure can be practiced without certain specific details.

[0023] The development process of ternary composite flood control is divided into six different stages: blank water flooding, pre-installed polymer protection slug, ternary main slug, ternary secondary slug, subsequent polymer protection slug, and subsequent water flooding. Figure 1 As shown, the multi-point sterilization method of this application selects different bactericide application locations according to the different stages, as detailed below:

[0024] (1) During the blank water drive stage and the subsequent water drive stage, the bactericide dosing point is set on the sewage station's external pipeline. The bactericide device is combined with the bactericide in a physical + chemical bactericide manner. The bactericide device adopts the ultraviolet bactericide process commonly used in oil fields. The bactericide is a high-concentration anti-corrosion bactericide, preferably an organic bromine compound bactericide. The bactericide dosing concentration is determined according to the conventional technology in the field and the bacterial content in the on-site water quality. In this embodiment, the bactericide dosing concentration is 10 mg / L.

[0025] (2) In the pre-polymer protection slug stage and the subsequent polymer protection slug stage, the "polymer prepared with clean water and polymer diluted with sewage" injection method is adopted; the bactericide dosing point is set at the inlet of the water injection pump of the water injection station, and a high-concentration anti-corrosion bactericide is used, preferably an organic bromine compound bactericide. The dosage of bactericide is determined according to the conventional technology in the field and the on-site adhesion loss. In this embodiment, the dosage of bactericide is 20 mg / L.

[0026] (3) Due to the long pipeline transportation distance between sewage station 1 and water injection station 2, the problem of bacterial regeneration will occur. The increase in the number of bacteria will inevitably lead to the problem of reduced viscosity. Therefore, in the pre-polymer protection slug stage and the subsequent polymer protection slug stage, the dosing point of the bactericide will be changed from the traditional sewage station 1 to the water injection station 2.

[0027] (4) In the ternary main slug stage and the ternary secondary slug stage, the ternary produced wastewater is mixed with polymer and the ternary produced wastewater is diluted with ternary composite flooding system for injection. The bactericide dosing point is set on the low-pressure uni-unit pipeline of the binary mixing station. High-concentration anti-corrosion bactericide is used, preferably an organic bromine compound bactericide. The bactericide dosage is determined according to the conventional technology in the field and the on-site viscosity loss. In this embodiment, the bactericide dosage is 10-30 mg / L.

[0028] Through indoor research and analysis of viscosity loss causes, it was found that when preparing the original system for displacement using ternary composite flooding produced water, the presence of n-butanol in surfactants such as alkylbenzene sulfonates in the ternary produced water dilution water easily acts as a nutrient for bacteria, accelerating bacterial growth and leading to a decrease in the viscosity of the polymer prepared at the mixing station. Adding a bactericide to the prepared wastewater can reduce the bacterial content and effectively improve the polymer viscosity stability to over 70%. Therefore, the bactericide dosing point is set at the low-pressure unary pipeline of the binary mixing station, where a high concentration of an organic bromine-based antiseptic bactericide is added.

[0029] In this embodiment of the disclosure, in order to reduce construction investment, the dosing device adopts a skid-mounted device, which can be relocated and reused repeatedly according to different injection stages.

[0030] This disclosure takes the injection well in the North 1-2 East Weak Alkali Ternary Composite Flooding Block as an example to describe in detail the multi-point chemical dosing method of this disclosure, so as to further illustrate the feasibility of the inventive concept of this method, the advanced nature of the inventive effect and the rationality of the technical solution, thereby helping to understand the method of this disclosure.

[0031] The North 1st and 2nd Drainage East Weak Alkaline Ternary Composite Flooding Block has ** injection wells, which were injected in September 2015 and will enter the subsequent water flooding stage in December 2024. Wastewater in this block is supplied by the Zhongshiqi Deep Wastewater Treatment Plant, high-pressure water by the Juzhongshier Water Injection Plant, binary liquid by the Zhong202 Binary Mixing Plant, and polymer mother liquor by the Sazhonger Preparation Plant. To ensure that the polymer viscosity loss in the block is within 20%, the multi-point sterilization method disclosed herein is used, with dosing points set according to different injection stages throughout the injection process. The specific dosing process is as follows:

[0032] (1) January 2015 - August 2015: Blank Water Drive Phase

[0033] The blank water drive uses ordinary sewage injection, with the dosing point located at the Zhongshiqi deep sewage station. It adopts the "sterilization device + chemical sterilization" method commonly used in this field. The physical sterilization device is the ultraviolet sterilization process commonly used in oil fields, and the sterilizing agent is a high-concentration anti-corrosion sterilizing agent, an organic bromine compound sterilizing agent commonly used in oil fields, with a dosage of about 10 mg / L.

[0034] (2) September 2015 - December 2015: Pre-polymer slug stage

[0035] The pre-polymer slug stage adopts the injection method of "polymer prepared with clean water + polymer diluted with sewage", and uses a high concentration of organic bromine compound bactericide as a disinfectant. Before adopting the method of this application, the disinfectant dosing point was set at the Zhongshiqi deep sewage station. When the dosing concentration was 20 mg / L, the block adhesion loss reached 28%.

[0036] According to the method of this application, considering the long pipeline transportation distance between the sewage treatment plant and the water injection station, and the problem of reduced viscosity due to bacterial regeneration, the dosing point is adjusted to the Juzhong Twelve Water Injection Station. When the type of bactericide added remains unchanged and the concentration is still 20 mg / L, the viscosity of the block can be kept within 20%.

[0037] (3) January 2016 - June 2019: Three-way block stage

[0038] The ternary sluice gate stage adopts the injection method of "wastewater-prepared polymer + wastewater-diluted ternary composite flooding system", and uses high-concentration antiseptic and bactericide organic bromine compound bactericide; before February 2017, the bactericide dosing point was the Polymer 12 water injection station, and the dosing concentration was 20mg / L, and the viscosity loss of the North 1 and 2 discharges increased to 35%.

[0039] Through indoor research and analysis of viscosity loss causes, it was found that when preparing the original system of ternary composite flooding produced water, the surfactants such as alkylbenzene sulfonates in the ternary produced water dilution water contain n-butanol, which easily acts as a nutrient for bacteria and accelerates bacterial reproduction. This leads to a decrease in polymer viscosity during preparation at preparation station 4. However, adding bactericides to the ternary produced water used for preparation can reduce the bacterial content and effectively improve the polymer viscosity stability to over 70%.

[0040] Following the method described in this application, the dosing point was adjusted in February 2017. A high-concentration organic bromine compound bactericide was added to the low-pressure unary pipeline at the Xinzhong 202 binary mixing station, with a concentration of 10-30 mg / L (adjusted according to water quality conditions). After the addition of the bactericide, the viscosity loss of the North 1-2 drainage outlet decreased from 35% to 17.95%, and during the ternary sluice blockage stage, the viscosity loss of the block was controlled below 20%.

[0041] (4) June 2019 - Present: Subsequent Polymer Slug Stage

[0042] The pre-polymer slug stage adopts the injection method of "polymer prepared with clean water + polymer diluted with deep oxygenated water", and uses high-concentration anti-corrosion and bactericide organic bromine compound bactericide; the dosing point is readjusted back to the No. 12 polymer injection station, and the dosing concentration remains at 20mg / L, during which the block viscosity loss is 20%.

[0043] After the above-described multi-point dosing process, the economic benefits of using the dosing method disclosed herein are analyzed as follows:

[0044] According to indoor studies, bacteria reduce polymer viscosity by 11%-17%, while production experience suggests a reduction of 13%-20%. Based on a multi-effect viscosity loss of 13%, if... Figure 2 As shown, based on the viscosity curve, to achieve the same viscosity, the wellhead concentration needs to be increased by about 6.5%, which means that to meet the development injection requirements, an additional 6.5% of polymer needs to be consumed.

[0045] The total dry powder consumption during the development phase of the weakly alkaline ternary composite flooding project in the North 1 and 2 rows was 18,996 tons. After applying this method, the viscosity loss during the sterilization process was controlled within 20%, ensuring the injection viscosity. Based on the calculation that a 13% viscosity loss would result in an additional 6.5% consumption of polymer dry powder, the North 1 and 2 rows east weakly alkaline ternary composite flooding project cumulatively saved 1,196.74 tons of dry powder. At a polymer dry powder price of 13,000 yuan / ton, this translates to a cumulative saving of 15,576,200 yuan in polymer dry powder costs. Because the multi-point dosing method of this invention only adjusts the dosing points according to different injection stages, without increasing the dosing concentration, the total production cost saved during the use of this method is 15,576,200 yuan.

[0046] It is understood that the various method embodiments mentioned above in this disclosure can be combined with each other to form combined embodiments without violating the principle and logic. Due to space limitations, this disclosure will not elaborate further.

[0047] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A multi-point bactericidal method for inhibiting viscosity loss of oilfield ASP polymer, characterized in that, include: In the blank water drive stage and subsequent water drive stage of the ternary composite flooding, the bactericide dosing point is located on the sewage treatment plant's external pipeline; in the pre-polymer slug stage and subsequent polymer protection slug stage, the bactericide dosing point is located at the inlet of the water injection pump of the water injection station; in the ternary main slug stage and ternary auxiliary slug stage, the bactericide dosing point is located on the low-pressure unary pipeline of the binary mixing station.

2. The multi-point sterilization method for suppressing viscosity loss of ternary composite flooding polymers in oilfields according to claim 1, characterized in that: In the pre-polymer slug stage and the subsequent polymer protection slug stage, a method of injecting polymer prepared with clean water and diluted with wastewater is adopted.

3. The multi-point sterilization method for suppressing viscosity loss of ternary composite flooding polymers in oilfields according to claim 2, characterized in that: In the ternary main slug stage and the ternary secondary slug stage, an injection method is adopted that combines ternary produced wastewater with polymer preparation and ternary produced wastewater dilution of the ternary composite flooding system.

4. The multi-point sterilization method for inhibiting viscosity loss of ternary composite flooding polymers in oilfields according to any one of claims 1-3, characterized in that: In the blank water drive stage and the subsequent water drive stage, a sterilization method combining a sterilization device and a sterilizing agent is adopted. The sterilization device adopts ultraviolet sterilization process, and the sterilizing agent adopts high-concentration preservative sterilizing agent.

5. The multi-point sterilization method for suppressing viscosity loss of ternary composite flooding polymers in oilfields according to claim 4, characterized in that: The high-concentration preservative and bactericide is an organic bromine compound bactericide.

6. The multi-point sterilization method for suppressing viscosity loss of ternary composite flooding polymers in oilfields according to claim 5, characterized in that: Organic bromine compounds are used as bactericides in both the pre-polymer slug stage and the subsequent polymer protection slug stage.

7. The multi-point sterilization method for suppressing viscosity loss of ternary composite flooding polymers in oilfields according to claim 6, characterized in that: Organic bromine compound bactericides are used in both the ternary main slug stage and the ternary secondary slug stage.

8. The multi-point sterilization method for suppressing viscosity loss of ternary composite flooding polymers in oilfields according to claim 6, characterized in that: The bactericide is added using a skid-mounted dosing device.

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