阅读说明：本技术 一种利用钻井液实现井筒降温与热能利用相结合的方法 (Method for realizing combination of shaft cooling and heat energy utilization by using drilling fluid ) 是由 肖东 陈伟雄 胡艺凡 李皋 孟英峰 李永杰 许佳欣 靖润昌 万里平 刘宇涵 石靖 于 2021-02-02 设计创作，主要内容包括：本发明涉及一种利用钻井液实现井筒降温与热能利用相结合的方法,包括：将复合相变蓄热材料与钻井液配制成蓄热复合钻井液,其从钻杆内流入,从喷射式钻头流出到达井底,携带岩屑通过环空返回地面,经分离出岩屑颗粒后进入换热器,换热器降低蓄热复合钻井液的温度使复合相变材料达到其凝固点,凝固后再循环利用,其中放出的热量被冷却水所吸收,吸热后的冷却水可作为钻井井场生活热水,实现热能利用的目的。该钻井液通过钻杆内时,随着地层温度逐渐增加,井筒内温度也逐渐增加,达到相变温度,复合相变材料开始蓄热,吸收来自地层传递的能量,从而达到降低井下井筒温度的目的。(The invention relates to a method for realizing combination of shaft cooling and heat energy utilization by using drilling fluid, which comprises the following steps: the composite phase change heat storage material and the drilling fluid are prepared into heat storage composite drilling fluid, the heat storage composite drilling fluid flows in from a drill rod, flows out from a jet type drill bit to reach the bottom of a well, carries rock debris to return to the ground through an annular space, the rock debris particles are separated out and then enter a heat exchanger, the heat exchanger reduces the temperature of the heat storage composite drilling fluid to enable the composite phase change material to reach the freezing point of the composite phase change material, the composite phase change material is recycled after solidification, the released heat is absorbed by cooling water, and the cooling water after heat absorption can be used as life hot water of a drilling well site. When the drilling fluid passes through the drill rod, the temperature in the shaft is gradually increased along with the gradual increase of the temperature of the stratum to reach the phase change temperature, the composite phase change material starts to store heat and absorb the energy transferred from the stratum, and therefore the purpose of reducing the temperature of the underground shaft is achieved.)

1. A method for realizing combination of shaft cooling and heat energy utilization by using drilling fluid is characterized by comprising the following steps:

preparing the composite phase-change heat storage material and the drilling fluid into heat storage composite drilling fluid;

the heat storage composite drilling fluid flows in from the drill rod, flows out from the jet drill bit to the well bottom, carries rock debris to return to the ground through an annular space, separates rock debris particles and then enters the heat exchanger, the heat exchanger reduces the temperature of the heat storage composite drilling fluid to enable the composite phase change material to reach the freezing point of the composite phase change material, the composite phase change material is condensed to release heat and then is recycled, the released heat is absorbed by cooling water, and the cooling water after absorbing heat can be used as life hot water of the well site.

2. The method for combining shaft cooling and heat energy utilization by using the drilling fluid as claimed in claim 1, wherein the composite phase change heat storage material is encapsulated by microcapsules if the composite phase change heat storage material has strong corrosivity, toxicity and volatility, or the components of the composite phase change heat storage material and the drilling fluid are subjected to chemical reaction.

3. The method for combining wellbore cooling and heat energy utilization by using the drilling fluid as claimed in claim 2, wherein the microencapsulation is micron-scale particles formed by coating a composite phase change heat storage material with a film-forming material.

4. The method for combining shaft cooling and heat energy utilization by using the drilling fluid as claimed in claim 1, wherein the composite phase change heat storage material starts phase change heat storage when reaching a phase change temperature in a drill pipe, changes from a solid to a liquid, absorbs energy transferred from a formation, and reduces the temperature of a downhole shaft; in the ground-based heat exchanger, the phase-change heat storage material condenses from a liquid to a solid.

5. The method for combining shaft cooling and heat energy utilization by using the drilling fluid as claimed in claim 1, wherein the phase change temperature of the composite phase change heat storage material is determined by the molar ratio of the components, and the composite phase change heat storage material is preferably prepared into nano-scale particles according to the temperature of a downhole shaft.

6. The method for combining borehole cooling and heat energy utilization by using drilling fluid as claimed in any one of claims 1 to 5, wherein the composite phase change heat storage material is (NaNO)₃-NaNO₂)/MgO。

7. The method for combining borehole cooling and heat energy utilization by using the drilling fluid as claimed in any one of claims 1 to 5, wherein the composite phase change heat storage material is NaOH/KOH.

Technical Field

The invention relates to the technical field of petroleum drilling, in particular to a method for realizing combination of shaft cooling and heat energy utilization by using drilling fluid.

Background

With the continuous and deep development of oil and gas development, oil and gas drilling gradually turns to deep stratum. In contrast to the fact that the development degree of shallow oil in the world is close to saturation, the near-surface oil gas resource discovery rate is rapidly reduced, and the newly increased reserves of deep oil gas show an obvious increasing trend. In order to meet the world energy demand, the search for oil and gas to the deep part of the stratum becomes an important guarantee for guaranteeing the sustainable development of the economic society of various countries.

At present, the drilling depth of China can reach 8882 meters at the deepest, and the underground temperature can reach 200 ℃. Affected by high temperatures, exceeding 150 ℃, the drilling technique presents the following fatal drawbacks: failure of electronic instruments and tools while drilling occurs at high temperature; (II) the service life of the drill bit is greatly reduced; (III) the corrosion rate increases exponentially, even leading to reduced yield strength of the drill pipe and premature failure; and (IV) the suspension capability of the drilling fluid is poor. The ultra-high temperature brings great difficulty to the development of resources, and hinders the development of petroleum drilling to a deeper well.

The phase change material is a functional material of the existing hot door, and in the process of storing and releasing energy, the temperature is kept unchanged or stabilized within a certain temperature range, so that the phase change material not only can realize heat storage, but also has a temperature regulation function, and the composite phase change material becomes a research hotspot due to the properties of various single materials, large latent heat, high heat conductivity and other excellent performances. The temperature of a downhole well bore exceeds 150 ℃, the drilling technology has fatal defects, and the used material is preferably a medium-temperature composite phase-change heat storage material. The composite phase change heat storage material can solve the problem of underground heat damage, and can also utilize heat energy absorbed by drilling fluid from the bottom of a well in the drilling process.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for realizing combination of shaft cooling and heat energy utilization by using drilling fluid, aiming at reducing the temperature of a shaft under the well by using heat storage when a composite phase change heat storage material is subjected to phase change, so that the temperature under the well is maintained within an acceptable range, and the heat energy absorbed by the drilling fluid from the bottom of the well in the drilling process can be utilized, so that the shaft cooling and the heat energy utilization in the drilling process are carried out simultaneously. The method is simple to operate and easy to popularize.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

a method for realizing combination of shaft temperature reduction and heat energy utilization by using drilling fluid comprises the following steps: preparing the composite phase-change heat storage material and the drilling fluid into heat storage composite drilling fluid; the heat storage composite drilling fluid flows in from a drill rod, flows out from a jet type drill bit to reach the bottom of a well, carries rock debris to return to the ground through an annular space, rock debris particles are separated out through a vibrating screen, a sand remover, a mud remover, a centrifugal machine and the like, then the rock debris particles enter a heat exchanger, the heat exchanger reduces the temperature of the heat storage composite drilling fluid to enable the composite phase change material to reach the freezing point of the composite phase change material, the composite phase change material is recycled after solidification, the released heat is absorbed by cooling water, and the cooling water can be used as daily life hot water of.

If the composite phase-change heat storage material has strong corrosivity, toxicity and volatility, or the components of the composite phase-change heat storage material and the drilling fluid are subjected to chemical reaction, the composite phase-change heat storage material is encapsulated by microcapsules for use.

The microcapsule encapsulation is micron-level particles formed by coating the composite phase change heat storage material with a film-forming material.

The composite phase-change heat storage material reaches the phase-change temperature in the drill rod and starts phase-change heat storage, the solid is changed into liquid, the energy transferred from the stratum is absorbed, and the temperature of the underground shaft is reduced; in the ground-based heat exchanger, the phase-change heat storage material condenses from a liquid to a solid.

The phase-change temperature of the composite phase-change heat storage material is determined by the molar ratio of the components, and the composite phase-change heat storage material is optimized according to the temperature of an underground shaft to be made into nano-scale particles.

The heat exchanger has good heat exchange capacity and can prevent blockage, the composite phase change heat storage material can be completely condensed into solid particles, and cooling water can be used as daily life hot water of a drilling well site after absorbing heat of the condensed position of the composite phase change heat storage material.

The composite phase change heat storage material is (NaNO)₃-NaNO₂) and/MgO. The composite phase change heat storage material is NaOH/KOH. (NaNO)₃-NaNO₂) the/MgO is a composite medium-temperature heat storage brick system, the phase transition temperature is 150-450 ℃, the heat storage capacity (447 +/-2) kJ/kg, and the corrosivity is low; the phase change temperature of NaOH/KOH is 145-318 ℃, the latent heat of phase change is 231kJ/kg, the specific heat capacity is 1.308kJ/(kg DEG C), and the corrosion resistance is realized.

When the heat storage composite drilling fluid passes through the drill stem, the temperature in the drill stem is gradually increased along with the gradual increase of the temperature of the stratum, and when the phase change temperature is reached, the phase change material starts phase change heat storage, absorbs energy transferred from the stratum and reduces the temperature of the underground shaft.

The phase change form of the composite phase change heat storage material is preferably solid-liquid phase change material, the phase change latent heat is large, the corrosivity is small, or the corrosion is avoided, the toxicity and the volatility are avoided, the phase state energy is condensed into a solid state, and the recovery and the utilization of heat energy resources are facilitated.

The micro particles coated by the composite phase-change heat storage material have excellent physical characteristics, large specific area and high heat storage efficiency, and the problems of corrosion, phase separation and the like of the phase-change material are solved.

The heat-accumulating composite drilling fluid returns to the ground, and when rock debris particles are separated out through a vibrating screen, a sand remover, a mud remover, a centrifugal machine and the like, the used microcapsules are small enough, so that the heat-accumulating composite drilling fluid cannot be separated out together with the rock debris, and enters a heat exchanger together with the drilling fluid.

Because the temperature of the underground shaft exceeds 150 ℃, the drilling technology has some fatal defects, and in order to ensure that the temperature of the underground shaft does not exceed 150 ℃, the phase change temperature of the composite phase change heat storage material is preferably within the range of 100-300 ℃, namely the intermediate temperature phase change material (intermediate temperature PCM). The composite phase change material has the properties of multiple single materials, and has excellent performances of large latent heat, high thermal conductivity and the like, so the used material is preferably a medium-temperature composite phase change heat storage material.

Degree of freedom known from Gibbs phase lawFor binary systems, the phase law is simplified toIn the single-phase region, F ═ 3, the temperature, pressure, and composition can be varied independently. In the two-phase region, F ═ 2, can be selected as an independent variable, either temperature and pressure, or temperature (or pressure) and the composition of one phase. The preferred composite phase change heat storage material belongs to a binary system, and in a two-phase region, the temperature and the phase composition are taken as independent variables, namely oneAfter one variable is determined, another variable is determined. Therefore, when the molar ratio of the components of the composite phase change heat storage material is determined, the phase change temperature is determined accordingly. In short, the phase change temperature of the composite phase change heat storage material is determined by the molar ratio of the components.

The preparation process of the composite drilling fluid with the heat storage function is as follows:

due to (NaNO)₃-NaNO₂) the/MgO has no toxicity, no volatilization and little corrosivity, can be used as a drilling fluid treating agent to be mixed with the drilling fluid, and other components in the drilling fluid are not mixed with NaNO₃-NaNO₂A chemically reactive substance, a substance which does not chemically react with MgO, (NaNO)₃-NaNO₂) The phase transition temperature of/MgO is determined by the temperature at a point in the wellbore downhole, based on (NaNO)₃-NaNO₂) The drilling fluid is specifically prepared according to different molar ratios of MgO, and the prepared drilling fluid needs to meet the functions and properties of the drilling fluid.

The NaOH/KOH has corrosivity, so the NaOH/KOH can not be mixed with the drilling fluid for preparation, otherwise, tools and equipment such as a metal drill rod and the like can be corroded, and the NaOH/KOH is encapsulated by microcapsules for use.

Compared with the prior art, the invention has the advantages that:

the temperature is remarkably reduced, and the heat energy carried by the drilling fluid in the drilling process can be utilized; the phase change temperature of the composite phase change heat storage material is determinable and adjustable; the structure and the performance of the drilling tool are not changed; the operation is simple, and the practicability is strong.

Drawings

FIG. 1 is a schematic diagram of a drilling fluid circulation according to the present invention;

FIG. 2 is a binary system phase diagram according to the present invention;

FIG. 3 is a line graph of phase transition temperatures for different NaOH mass fractions according to the example;

FIG. 4 is a plot of example downhole temperature versus specific heat;

FIG. 5 is a graph showing the solidification of a 1:1 molar NaOH/KOH mixture under pressure for the examples.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings by way of examples.

As shown in fig. 1, the invention discloses a method for realizing combination of shaft temperature reduction and heat energy utilization by using drilling fluid, which comprises the following steps:

the composite phase change heat storage material and the drilling fluid are prepared into the heat storage composite drilling fluid with heat storage capacity.

If the composite phase change heat storage material has strong corrosivity, toxicity and other hazards or the components of the composite phase change heat storage material and other components of the drilling fluid are subjected to chemical reaction, the drilling fluid is encapsulated by microcapsules for use.

As shown in figure 1, the prepared heat storage composite drilling fluid flows in a drill rod, flows out of a jet type drill bit to reach the bottom of a well, carries rock debris to return to the ground through an annular space, rock debris particles are separated through a vibrating screen, a sand remover, a mud remover, a centrifugal machine and the like, then enters a heat exchanger, the heat exchanger reduces the temperature of the heat storage composite drilling fluid to enable a composite phase-change material to reach the freezing point of the composite phase-change material, the composite phase-change material is recycled after solidification, the released heat is absorbed by cooling water, and the cooling water can be used as hot water for daily life.

As shown in figure 2, when the heat-storage composite drilling fluid passes through the drill pipe, the temperature and the pressure in the shaft are gradually increased along with the gradual increase of the depth of the stratum to reach the phase transition temperature T₁And when the temperature is continuously increased, the composite phase-change material is converted from a solid phase to a liquid phase as shown by the direction of the right arrow of the figure, the composite phase-change material starts phase change and heat storage, the energy transferred from the stratum is absorbed, and the temperature of the underground shaft is reduced. When the temperature drops to T₂When the composite phase-change material is changed from a liquid phase to a solid phase, as shown by a left arrow in the figure, the composite phase-change material emits heat, and the emitted heat is absorbed by cooling water of the heat exchanger.

The cooling water of the heat exchanger is heated and then stored in the water storage tank, and can be supplied to a drilling well site to be used as hot water in daily life.

The phase change form of the composite phase change heat storage material is preferably solid-liquid phase change material, the phase change latent heat is large, the corrosivity is small, or the composite phase change heat storage material is non-corrosive, non-toxic and non-volatile, and the phase state can be solidified into a solid state, so that the composite phase change heat storage material is convenient to recycle.

Further, the microcapsule is a fine particle formed by coating a solid, liquid or gas with a film forming material, is composed of a core material and a wall material, has excellent physical properties, a large specific area, and high heat storage efficiency, and solves the problems of corrosion, phase separation, and the like of a phase change material itself.

The heat-accumulating composite drilling fluid returns to the ground, and when rock debris particles are separated by a vibrating screen, a sand remover, a mud remover, a centrifugal machine and the like, the used microcapsules are small enough, so that the heat-accumulating composite drilling fluid cannot be separated from the rock debris together, and enters a heat exchanger together with the drilling fluid.

The temperature of the underground shaft exceeds 150 ℃, so that the drilling technology has fatal defects, and in order to ensure that the temperature of the underground shaft does not exceed 150 ℃, the phase change temperature of the composite phase change heat storage material is in the range of 100-300 ℃, namely the intermediate temperature phase change material (intermediate temperature PCM). The composite phase change material has the properties of multiple single materials, and has excellent performances of large latent heat, high thermal conductivity and the like, so the used material is preferably a medium-temperature composite phase change heat storage material.

Degree of freedom known from Gibbs phase lawFor binary systems, the phase law is simplified toIn a single zone, F ═ 3, the temperature, pressure, and composition can be varied independently. In the two-phase region, F ═ 2, can be selected as an independent variable, either temperature and pressure, or temperature (or pressure) and the composition of one phase. The preferred composite phase change heat storage material is a binary system, in the two-phase region, with the temperature and phase composition as independent variables, after one variable is determined, the other variable is determined. Therefore, when the molar ratio of the components of the composite phase change heat storage material is determined, the phase change temperature is determined accordingly. In short, the phase change temperature of the composite phase change heat storage material is determined by the molar ratio of the components.

Preferably, two composite phases are selectedAs examples of the heat-accumulative material, respectively, (NaNO)₃-NaNO₂) MgO and NaOH/KOH.

(NaNO₃-NaNO₂) the/MgO is a composite medium-temperature heat storage brick system, the phase transition temperature is 150-450 ℃, the heat storage capacity (447 +/-2) kJ/kg, and the corrosivity is low; the phase change temperature of NaOH/KOH is 145-318 ℃, the latent heat of phase change is 231kJ/kg, the specific heat capacity is 1.308kJ/(kg DEG C), and the corrosion resistance is realized.

The preparation process of the drilling fluid with phase change heat storage is as follows:

due to (NaNO)₃-NaNO₂) the/MgO has no toxicity, no volatilization and little corrosivity, can be used as a drilling fluid treating agent to be mixed with the drilling fluid, and other components in the drilling fluid are not mixed with NaNO₃-NaNO₂A chemically reactive substance, a substance which does not chemically react with MgO, (NaNO)₃-NaNO₂) The phase transition temperature of/MgO is determined by the temperature at a point in the wellbore downhole, based on (NaNO)₃-NaNO₂) The drilling fluid is specifically prepared according to different molar ratios of MgO, and the prepared drilling fluid needs to meet the functions and properties of the drilling fluid.

The NaOH/KOH has corrosivity, so the NaOH/KOH can not be mixed with the drilling fluid for preparation, otherwise, tools and equipment such as a metal drill rod and the like can be corroded, and the NaOH/KOH is encapsulated by microcapsules for use.

Compared with the prior art, the invention has the advantages that:

the temperature is remarkably reduced, and the heat energy carried by the drilling fluid in the drilling process can be utilized; the phase change temperature of the composite phase change heat storage material is determinable and adjustable; the structure and the performance of the drilling tool are not changed; the operation is simple, and the practicability is strong.

FIG. 3 is a line graph of phase transition temperatures corresponding to different mass fractions of NaOH, and it can be seen visually that when the mass fraction of NaOH is greater than 23.4%, the phase transition temperature increases with the increase of the mass fraction of NaOH, and the amount of NaOH can be increased gradually to increase the phase transition temperature.

FIG. 4 is a graph showing the relationship between the downhole temperature and the specific heat, and it can be seen from the graph that the specific heat of the drilling fluid can be increased by 50% by using the composite phase-change heat storage material according to the present technology, and the downhole temperature can be reduced by about 30 ℃.

FIG. 5 is a graph showing the solidification of a 1:1 molar NaOH/KOH mixture under pressure, and it can be seen that as time goes by, the 1:1 NaOH/KOH mixture reaches a phase transition temperature of 184.2 deg.C, the mixture starts to accumulate heat and changes from solid to liquid, until 151.2 deg.C, the mixture starts to exothermically solidify, changes from liquid to solid, and when 84.1 deg.C, the mixture has a solid-to-solid phase transition. The exothermic process of the binary NaOH/KOH system therefore includes solid-liquid phase change and solid-solid phase change processes. If the composite phase-change heat storage material is not encapsulated by the microcapsules, the temperature can be reduced through a heat exchanger according to a solidification curve, and the composite phase-change heat storage material is recovered after solidification and is recycled.

Table 1 shows the phase transition temperatures of NaOH and KOH in different molar ratios, and as shown in table 1, the phase transition temperatures can be determined according to the different amounts of the two, and the amount ratio of the two is determined by the downhole wellbore temperature.

TABLE 1 phase transition thermometer with different molar ratios of NaOH to KOH

The principle of the invention is as follows: a method for realizing the combination of shaft cooling and heat energy utilization by using drilling fluid is mainly characterized in that a heat storage composite drilling fluid is prepared by using a composite phase change heat storage material and the drilling fluid; when the heat storage composite drilling fluid passes through the drill stem, the phase change temperature is reached, heat storage is started, and energy transferred from the stratum is absorbed, so that the aim of reducing the temperature of a shaft is fulfilled. The heat energy carried by the drilling fluid in the drilling process can be utilized on the ground, so that the drilling and the heat energy utilization can be carried out simultaneously. The composite phase-change heat storage material is preferably selected according to phase-change temperature, heat storage capacity, nontoxicity, nonvolatility, non-corrosiveness, non-reaction with drilling fluid and the like, and the phase-change temperature of the composite phase-change heat storage material is determined according to the molar ratio of the components. The method has the advantages that the temperature is obviously reduced, and the heat energy carried by the drilling fluid in the drilling process can be utilized; the phase change temperature of the composite phase change heat storage material is determinable and adjustable; the structure and the performance of the drilling tool are not changed; the operation is simple, and the practicability is strong.

It will be appreciated by those of ordinary skill in the art that the two composite phase change heat storage materials described herein are intended to aid the reader in understanding the manner of practicing the invention, and it is to be understood that the scope of the invention is not limited to such specific statements and examples. Those skilled in the art can make numerous other specific variations and combinations in accordance with the teachings of the present disclosure without departing from the spirit or scope thereof.