WO2022237777A1

WO2022237777A1 - Method for reinforcing natural gas hydrate reservoir

Info

Publication number: WO2022237777A1
Application number: PCT/CN2022/091976
Authority: WO
Inventors: 王誉泽; 杨建宇
Original assignee: 南方科技大学
Priority date: 2021-05-12
Filing date: 2022-05-10
Publication date: 2022-11-17
Also published as: CN113202444A

Abstract

The present invention relates to a method for reinforcing a natural gas hydrate reservoir. The natural gas hydrate reservoir comprises an upper covering layer (1) and a lower covering layer (2), wherein a hydrate region (3) for natural gas hydrate occurrence is arranged between the upper covering layer (1) and the lower covering layer (2), and a seepage channel (4) is present in the hydrate region (3). The method comprises: injecting a microbial solution capable of improving alkalinity and promoting generation of carbonate into a seepage channel (4) of a hydrate region; and after the injection of the microbial solution capable of improving alkalinity and promoting generation of the carbonate, injecting a cement liquid into the seepage channel (4) of the hydrate region at an interval of a first preset time length, such that the cement liquid reacts with the microbial solution capable of improving alkalinity and promoting generation of the carbonate to generate sediment (6). By means of the method, the effects of expanding a reinforcing range of an argillaceous silty sand hydrate reservoir, reinforcing the argillaceous silty sand hydrate reservoir and also improving the permeability of the argillaceous silty sand hydrate reservoir, reducing the heterogeneity of a reinforcement effect of the hydrate reservoir along with change of a horizontal distance, and improving grain size distribution of the hydrate and a composition proportion of a soil body can be achieved.

Description

A method for strengthening natural gas hydrate reservoir

This application claims the priority of the Chinese patent application with the application number 202110520352.X and the application title "A Natural Gas Hydrate Reservoir Strengthening Method" filed with the China Patent Office on May 12, 2021, the entire contents of which are incorporated by reference in application.

technical field

The application relates to the technical field of marine resources and basic engineering, in particular to a method for reinforcing natural gas hydrate reservoirs.

Background technique

Natural gas hydrate is a cage compound formed by methane and other hydrocarbon gases and water under high pressure and low temperature conditions. As a new type of clean combustion energy, it has the characteristics of high combustion density, wide distribution range and high content, and has become one of the hot spots in the field of energy science research. Existing exploration results show that natural gas hydrates are mainly distributed in the arctic permafrost and the deep water area of 300-3000 m deep in the coastal continental shelf. Preliminary estimates indicate that the global natural gas hydrate resources are about 21×1015 m3, and the resources are the global carbon-containing compounds. Twice of that, about 95% of which occur in the deep sea. The natural gas hydrate in the Shenhu area of the South my country Sea belongs to the argillaceous silt type reservoir type, which accounts for more than 90% of the world's resources. Therefore, strengthening the argillaceous siltstone clay is of great significance for the safe and efficient exploitation of hydrates.

The existing reinforcement of natural gas hydrate reservoirs is mainly to inject cement slurry through the wellbore or artificially drilled small holes, and use the strength increase of cement to strengthen the hydrate reservoir. However, due to the high density of cement slurry and the mud Silt reservoirs have low permeability, and usually only cement stones with high strength will be formed in a small area near the wellbore and slimhole to strengthen the reservoir. The high-strength cement stone supports the formation near the wellbore. This method, on the one hand, can only reinforce the natural gas hydrate reservoir near the well, resulting in a limited reinforcement range and uneven reinforcement effect of the gas hydrate reservoir extending from the wellbore wall to the reservoir; on the other hand, the use of cement The way of pouring reinforcement will reduce the permeability of hydrate reservoirs and affect the production capacity of hydrates. At the same time, the heat generated by cement solidification will cause hydrates to decompose, which may affect the stability of hydrate reservoirs reinforcement.

The above content is only used to assist in understanding the technical solution of the present application, and does not mean that the above content is admitted as prior art.

technical problem

The main purpose of the present application is to provide a natural gas hydrate reservoir strengthening method, aiming at improving the existing natural gas hydrate reservoir technology.

technical solution

To achieve the above purpose, the present application provides a natural gas hydrate reservoir reinforcement method, the natural gas hydrate reservoir includes an upper overburden layer and a lower overburden layer, and the upper overburden layer and the lower overburden layer are endowed A hydrate zone where natural gas hydrates are stored, where seepage channels exist in the hydrate zone, and the natural gas hydrate reservoir reinforcement method includes:

Injecting a microbial solution that can increase alkalinity and promote carbonate formation into the percolation channel of the hydrate zone;

After the microbial solution that can increase the alkalinity and promote the formation of carbonate radicals is injected, the cementing fluid is injected into the percolation channel of the hydrate zone at intervals of a first preset period of time, so that the cementing fluid and the microbial solution generate The reaction produced a precipitate.

In one embodiment, the step of injecting the microbial solution that can increase the alkalinity and promote the production of carbonate radicals into the percolation channel of the hydrate zone includes:

constructing a communication channel connecting the offshore platform and the seepage channel of the hydrate zone;

The configured microbial solution that can increase the alkalinity and promote the generation of carbonate is injected from the offshore platform along the communication channel into the percolation channel of the hydrate zone.

In one embodiment, the step of constructing a communication channel connecting the offshore platform and the seepage channel of the hydrate zone includes:

The offshore drilling platform and ocean drilling technology are used for drilling construction to form the drilling process, the upper end of the drilling process communicates with the offshore platform, and the lower end of the drilling well extends into the lower overburden.

In one embodiment, the depth of the drilling into the lower overburden is 1/20-1/5 of the thickness of the hydrate zone.

In one embodiment, the microbial solution that can increase the alkalinity and promote the generation of carbonate includes a liquid of Bacillus pasteurianus.

In one embodiment, the natural gas hydrate reservoir reinforcement method further includes:

The cementing liquid is injected into the seepage channel of the hydrate zone along the communication channel at intervals of a second preset time period.

The step of injecting the cementing liquid into the seepage channel of the hydrate zone along the communication channel is repeated for a preset number of times at the interval of a second preset time.

In one embodiment, the preset times are 10-12 times.

In one embodiment, the communication channel is communicated with a booster pump;

The step of injecting the configured microbial solution that can increase the alkalinity and promote the production of carbonate from the offshore platform along the communication channel to the seepage channel of the hydrate zone includes:

start the booster pump;

The configured microbial solution that can increase the alkalinity and promote the formation of carbonate radicals is injected into the percolation channel of the hydrate zone along the communication channel in the form of high pressure.

In one embodiment, after repeating the step of injecting the cementing liquid into the seepage channel of the hydrate zone along the communication channel for a preset number of times by setting the interval for a second preset time, further comprising: :

Well logging technology was used to evaluate the changes of porosity, permeability, Poisson's ratio and elastic modulus of hydrate reservoirs before and after reinforcement.

Beneficial effect

In the technical solution of the present application, by injecting the microbial solution into the seepage channel of the hydrate zone, it can flow and diffuse along the seepage channel of the hydrate zone, thereby uniformly distributing the microbial solution in the natural gas hydration zone. Then inject cementing fluid into the seepage channel of the hydrate zone, and the microbial solution hydrolyzes urea in the natural gas hydrate reservoir to generate a large amount of carbonate ions, which then undergoes a precipitation reaction with the cementing fluid. Calcium carbonate precipitation completes the reinforcement of the natural gas hydrate reservoir. Compared with the traditional form of cement pouring, the technical solution of this application expands the reinforcement range of the natural gas hydrate reservoir, and the reaction has no heat release, maintaining the stability of the hydrate reservoir Moreover, due to the continuous increase of the total amount of calcium carbonate precipitation and the continuous growth of crystal particles in the seepage pores of the hydrate reservoir, the particle size distribution and soil composition ratio of the original muddy silt hydrate reservoir are improved, and the hydration rate is promoted. Improvement of the seepage capacity of the reservoir.

Description of drawings

Fig. 1 is a schematic structural diagram of the operating environment involved in the embodiment scheme of the present application;

Fig. 2 is a schematic flow chart of the first embodiment of the natural gas hydrate reservoir strengthening method of the present application;

Fig. 3 is a schematic flow chart of the second embodiment of the natural gas hydrate reservoir strengthening method of the present application;

Fig. 4 is a schematic flow chart of the third embodiment of the natural gas hydrate reservoir strengthening method of the present application;

Fig. 5 is a schematic flowchart of a fourth embodiment of the natural gas hydrate reservoir strengthening method of the present application.

The realization, functional features and advantages of the present application will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

Explanation of reference numbers:

标号 label	名称 name	标号 label	名称 name
1 1	上覆盖层1 top cover 1	2 2	下覆盖层2 lower cover 2
3 3	水合物区3 Hydrate zone 3	4 4	渗流通道4 percolation channel 4
5 5	钻井5 drilling 5	6 6	沉淀6 Precipitation 6
7 7	海水7 sea water 7	the	the

Embodiments of the present invention

It should be understood that the specific embodiments described here are only used to explain the present application, not to limit the present application.

Referring to Fig. 1, the natural gas hydrate reservoir includes an upper overburden 1 and a lower overburden 2, and between the upper overburden 1 and the lower overburden 2 is a hydrate zone 3 where gas hydrates occur, and the hydrate There is a seepage channel 4 in the object area 3. In this embodiment, the upper covering layer 1 is located at a sea depth of 1200m, the thickness of the upper covering layer 1 is 400m, the thickness of the hydrate area 3 is 270m, and the seabed temperature is At about 10°C, the seabed pressure is about 10 MPa, and there are seepage channels 4 in the hydrate zone 3, but it is not limited to this embodiment.

The embodiment of the present application provides a natural gas hydrate reservoir strengthening method. Referring to FIG. 2 , FIG. 2 is a schematic flowchart of a first embodiment of the natural gas hydrate reservoir strengthening method of the present application.

In this embodiment, the natural gas hydrate reservoir reinforcement method includes the following steps:

Step S10: injecting a microbial solution capable of increasing alkalinity and promoting carbonate formation into the percolation channel 4 of the hydrate zone 3;

It should be noted that there can be many kinds of microbial solutions that can increase the alkalinity and promote the generation of carbonate, as long as they can hydrolyze urea to produce carbonate ions, such as the commonly used Bacillus pasteurian solution, whose metabolism can produce and decompose urea The urease, the carbonate ion produced after the decomposition of urea, of course, can also be other microbial solutions that can achieve the same effect, such as urea micrococcus solution. Further, in order to make the microbial solution the easiest to obtain, the microbial solution that can increase the alkalinity and promote the generation of carbonate includes the Bacillus pasteurian liquid. In order to facilitate the understanding of the technical scheme of the present application, in this embodiment, the alkaline The microbial solution that promotes the generation of carbonate mainly refers to the Bacillus pasteurian solution, the concentration OD600 is 1.0, and the urea hydrolysis efficiency is 20-40 mM/h.

Through step S10, the microbial solution that can increase the alkalinity and promote the generation of carbonate is injected into the percolation channel 4 of the hydrate zone 3. Compared with the solution of pouring cement, injecting the microbial solution that can increase the alkalinity and promote the generation of carbonate , due to the nature of the solution, high-pressure injection can be used to make it cover a wider area, and the microbial solution can also flow and diffuse along the seepage channel 4 of the hydrate zone 3, so that the distribution is more extensive and uniform.

Step S20: after the injection of the microbial solution that can increase the alkalinity and promote the formation of carbonate radicals, inject the cementing liquid into the percolation channel 4 of the hydrate zone 3 at intervals of a first preset time interval, so that the cementing liquid and The microbial solution that can increase the alkalinity and promote the generation of carbonate reacts to form a precipitate 6 .

It should be noted that the diffusion of the microbial solution requires a certain amount of time, and the generation of carbonate ions also requires a certain amount of time. Therefore, it is necessary to inject the cementing liquid into the hydrate zone 3 after an interval of the first preset time. Seepage channel 4, so that the cementing fluid reacts with the carbonate ions produced by the microbial solution, and then produces precipitation 6 to complete the reinforcement of the natural gas hydrate reservoir. The first preset time here is generally 2 to 12 hours . Specifically, there can be many types of cementing liquid, such as calcium ion solution, magnesium ion solution, etc., in order to facilitate the understanding of the technical solution of the present application, in this embodiment, the cementing liquid refers to containing 0.5M calcium chloride, 0.75M A solution of urea and 3g/L beef extract.

In the scheme of this embodiment, the microbial solution is evenly distributed by injecting the microbial solution into the seepage channel 4 of the hydrate zone 3 so that it can flow and diffuse along the seepage channel 4 of the hydrate zone 3 In the natural gas hydrate reservoir, cementing fluid is then injected into the percolation channel 4 of the hydrate zone 3, and the microbial solution hydrolyzes urea in the natural gas hydrate reservoir to generate a large amount of carbonate ions, thereby forming a reaction with the cementing fluid. Precipitation reaction, through the calcium carbonate precipitation 6 generated by the reaction, the reinforcement of the natural gas hydrate reservoir is completed. Compared with the traditional form of cement pouring, the technical solution of this application expands the reinforcement range of the natural gas hydrate reservoir, and the reaction has no heat release , to maintain the stability of the hydrate reservoir, and, due to the continuous increase of the total amount of calcium carbonate precipitate 6 and the continuous growth of crystal particles in the percolation pores of the hydrate reservoir, the particle size of the original muddy silt hydrate reservoir is improved The distribution and proportion of soil components promote the improvement of the seepage capacity of hydrate reservoirs.

Referring to FIG. 3 , FIG. 3 is a schematic flowchart of a second embodiment of a natural gas hydrate reservoir strengthening method of the present application.

Based on the first embodiment above, the step S10 of the natural gas hydrate reservoir reinforcement method in this embodiment further includes:

Step S01: Construct a communication channel connecting the offshore platform and the seepage channel 4 of the hydrate zone 3;

Specifically, there are many forms of constructing communication channels, such as the seepage channel 4 directly connecting the offshore platform and the hydrate zone 3 through a riser. Furthermore, the most common and mature one, the S01 includes: The drilling 5 is constructed by adopting the offshore drilling 5 platform and the offshore drilling 5 technology to form the drilling 5 , the upper end of the drilling 5 communicates with the offshore platform, and the lower end of the drilling 5 extends into the lower covering layer 2 .

Further, the deep sea drilling 5 is carried out using the deep sea drilling 5 platform, the depth of the drilling 5 is related to the mechanical properties of the upper overburden 1, the lower overburden 2 and the hydrate zone 3, and the drilling 5 goes deep into the lower The depth of the overburden layer 2 is 1/20~1/5 of the thickness of the hydrate zone 3. Optimally, the depth of the drilling 5 penetrating into the lower overburden layer 2 is 1/5 of the thickness of the hydrate zone 3. 10. In this embodiment, the diameter of the opening of the borehole 5 is 1.5m, and the borehole 5 goes down to a depth of 20m in the lower overburden layer 2, and the diameter of the bottom of the well is reserved for 0.8m. Due to the complexity of deep-sea sediments, it is difficult to drill wells, so it is necessary to use multi-layer casing drilling technology, preferably using 6-layer casing drilling technology. The drilling fluid selected during drilling 5 must not only meet the basic requirements of the formation, but also be able to effectively prevent hydrate decomposition.

Step S02: Inject the configured microbial solution that can increase the alkalinity and promote the generation of carbonate from the offshore platform along the communication channel to the percolation channel 4 of the hydrate zone 3 .

In this embodiment, through the construction of communication channels, it is possible to effectively inject a large amount of microbial solutions and cementing fluids that can increase alkalinity and promote carbonate formation from the offshore platform into the seepage channel 4 of the hydrate zone 3, thereby completing the process. The hydrate zone 3 is consolidated.

Referring to FIG. 4 , FIG. 4 is a schematic flowchart of a third embodiment of a natural gas hydrate reservoir strengthening method of the present application.

Based on the second embodiment above, the natural gas hydrate reservoir strengthening method of this embodiment further includes:

Step S30: injecting the cementing liquid into the percolation channel 4 of the hydrate zone 3 along the communication channel at intervals of a second preset time period.

It is understandable that once the cementing fluid is injected, the amount of precipitation 6 produced is limited, and the effect of reinforcement is also limited. After the first cementing fluid is injected, microorganisms continue to produce carbonate ions. Therefore, the second preset time interval , the cementing fluid is injected into the percolation channel 4 of the hydrate zone 3 along the communication channel, so that the natural gas hydrate reservoir can be reinforced twice, so that the effect of reinforcement is better. It should be noted that the second preset time period here generally refers to about 24 hours, so as to allow enough time for the microbial solution to react with the cementing fluid.

Further, refer to FIG. 5 , which is a schematic flowchart of a fourth embodiment of a natural gas hydrate reservoir strengthening method of the present application.

After the step S30, a step S40 is further included: repeating the step of injecting the cementing liquid into the percolation channel 4 of the hydrate zone 3 along the communication channel for a preset number of times at the second preset time interval.

Through the above steps, the gas hydrate reservoir can be reinforced in multiple layers, and the reinforcement effect on the gas hydrate reservoir is further optimized. Of course, it is not possible to continuously strengthen the reinforcement effect on natural gas hydrate reservoirs by adding cementing fluid endlessly. After testing the surface for many times, after adding 10-12 times, the strengthening effect will no longer be Obviously, therefore, the preset number of times is 10-12 times.

In addition, there are many ways to inject the microbial solution and cementing fluid into the seepage channel 4, and it can be injected into the seepage channel 4 from the offshore platform, so as to utilize the gap between the offshore platform and the seepage channel 4. The height difference allows the microbial solution and cementing fluid to infiltrate and diffuse freely under the action of gravity. However, due to the low permeability of the muddy silt reservoir and part of the liquid column to balance the formation pressure, if gravity alone is used, the injection speed is relatively slow , in order to speed up the infiltration rate, the communication channel is connected with a booster pump, specifically, the booster pump can be arranged on the offshore platform, or inside the communication channel, if the booster pump is arranged in the For the interior of the communication channel, the liquid and solid particles in the communication channel will cause certain wear and tear on the booster pump, or the booster pump will hinder the liquid in the communication channel to a certain extent, and , the booster pump is not easy to replace, therefore, in this embodiment, the booster pump is set on the offshore platform; The step of injecting the platform into the percolation channel 4 of the hydrate zone 3 along the communication channel includes:

start the booster pump;

The configured microbial solution that can increase the alkalinity and promote the formation of carbonate radicals is injected into the seepage channel 4 of the hydrate zone 3 along the communication channel in the form of high pressure.

Thereby utilizing the height difference between the offshore platform and the seepage channel 4 and the double action of the booster pump to increase the infiltration speed and distance of the injected microbial solution and cementing fluid under the action of gravity and pressure difference of the high-pressure pump, thereby The range of reinforcement has been enhanced.

In addition, to check whether the reinforced hydrate reservoir reaches the standard, the step of injecting the cementing liquid into the percolation channel 4 of the hydrate zone 3 along the communication channel at the second preset time interval After repeating the steps a preset number of times, also include:

The logging technology here is an existing technology. It can adopt the method of acoustic wave time difference logging, nuclear magnetic logging, resistivity logging and other schemes. It will not be explained in detail here. Through the evaluation of the above parameters, it can be very intuitive The effect of previous reinforcement was detected, and then the quality evaluation system for MICP technology to strengthen and improve permeability hydrate reservoirs was established.

It should be understood that the above is only an example, and does not constitute any limitation to the technical solution of the present application. In a specific application, those skilled in the art can make settings according to needs, and the present application does not limit this.

It should be noted that the workflow described above is only illustrative and does not limit the scope of protection of this application. In practical applications, those skilled in the art can select part or all of them to implement according to actual needs. The purpose of the scheme of this embodiment is not limited here.

Furthermore, it should be noted that in this document, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or system comprising a set of elements includes not only those elements, but also other elements not expressly listed, or elements inherent in such a process, method, article, or system. Without further limitations, an element defined by the phrase "comprising a..." does not preclude the presence of additional identical elements in the process, method, article or system comprising that element.

The serial numbers of the above embodiments of the present application are for description only, and do not represent the advantages and disadvantages of the embodiments.

Through the description of the above embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus a necessary general-purpose hardware platform, and of course also by hardware, but in many cases the former is better implementation. Based on this understanding, the essence of the technical solution of this application or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product is stored in a storage medium (such as a read-only memory (Read Only Memory) , ROM)/RAM, magnetic disk, optical disk), including several instructions to enable a terminal device (which can be a mobile phone, computer, server, or network device, etc.) to execute the methods described in various embodiments of the present application.

The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. All equivalent structures or equivalent process transformations made by using the description of the application and the accompanying drawings are directly or indirectly used in other related technical fields. , are all included in the patent protection scope of the present application in the same way.

Claims

A natural gas hydrate reservoir strengthening method, wherein the natural gas hydrate reservoir includes an upper overburden and a lower overburden, and between the upper overburden and the lower overburden is a hydrate zone where natural gas hydrate occurs, There are seepage channels in the hydrate zone, and it is characterized in that the method for strengthening the natural gas hydrate reservoir includes:

Injecting a microbial solution that can increase alkalinity and promote carbonate formation into the percolation channel of the hydrate zone;

After the microbial solution that can increase the alkalinity and promote the formation of carbonate radicals is injected, the cementing fluid is injected into the percolation channel of the hydrate zone at intervals of a first preset period of time, so that the cementing fluid and the microbial solution generate The reaction produced a precipitate.
The natural gas hydrate reservoir strengthening method according to claim 1, wherein the step of injecting a microbial solution capable of increasing alkalinity and promoting carbonate formation into the seepage channel of the hydrate zone comprises:

constructing a communication channel connecting the offshore platform and the seepage channel of the hydrate zone;

The configured microbial solution that can increase the alkalinity and promote the generation of carbonate is injected from the offshore platform along the communication channel into the percolation channel of the hydrate zone.
The natural gas hydrate reservoir strengthening method according to claim 2, wherein the step of constructing a communication channel connecting the seepage channel between the offshore platform and the hydrate zone comprises:

The offshore drilling platform and ocean drilling technology are used for drilling construction to form the well, the upper end of the well communicates with the offshore platform, and the lower end of the well extends into the lower overburden.
The natural gas hydrate reservoir reinforcement method according to claim 3, characterized in that, the depth of the drilling into the lower overburden is 1/20-1/5 of the thickness of the hydrate zone.
The natural gas hydrate reservoir reinforcement method according to claim 2, characterized in that, the microbial solution that can increase the alkalinity and promote the formation of carbonate radicals comprises a liquid of Bacillus pasteurianus.
The natural gas hydrate reservoir reinforcement method according to claim 5, wherein the natural gas hydrate reservoir reinforcement method further comprises:

The cementing liquid is injected into the seepage channel of the hydrate zone along the communication channel at intervals of a second preset time period.
The natural gas hydrate reservoir reinforcement method according to claim 6, wherein the natural gas hydrate reservoir reinforcement method further comprises:

The step of injecting the cementing liquid into the seepage channel of the hydrate zone along the communication channel is repeated for a preset number of times at the interval of a second preset time.
The natural gas hydrate reservoir reinforcement method according to claim 7, wherein the preset number of times is 10 to 12 times.
The natural gas hydrate reservoir strengthening method according to claim 2, wherein the communication channel is connected with a booster pump;

The step of injecting the configured microbial solution that can increase the alkalinity and promote the production of carbonate from the offshore platform along the communication channel to the seepage channel of the hydrate zone includes:

start the booster pump;

The configured microbial solution that can increase the alkalinity and promote the formation of carbonate radicals is injected into the percolation channel of the hydrate zone along the communication channel in the form of high pressure.
The natural gas hydrate reservoir reinforcement method according to claim 7, characterized in that, the interval between the second preset time length, the cementing liquid is injected into the seepage flow of the hydrate zone along the communication channel After the step of the channel repeats the preset number of steps, it also includes:

Well logging technology was used to evaluate the changes of porosity, permeability, Poisson's ratio and elastic modulus of hydrate reservoirs before and after reinforcement.