Numerical simulation of temperature field in crack of supercritical carbon dioxide fracturing

Abstract

Supercritical carbon dioxide (SC-CO 2 ) fracturing technology has far-reaching application potential for unconventional resources which is beneficial to water protection and CO 2 sequestration. In this paper, temperature field in the crack of SC-CO 2 fracturing which will affect flow behavior of SC-CO 2 and the carrying capacity for proppants has been studied. A generalized and pragmatic numerical method coupled with the physical properties model of CO 2 and heat and mass transfer in the formation rock has been established to calculate the variations of temperature and density in the crack during fracturing. Porous medium model was used to describe the formation rock which would make the calculation more accurate. Rules of influence distance of the rock with time and injection displacement were analyzed. Distribution of temperature in XY plane is symmetrical, while temperature on the bottom wall is much less than that of the top wall in XZ plane. Decrease in injection temperature and increase in injection displacement will make the temperature of SC-CO 2 lower at the same position which is beneficial to the proppant transportation. Therefore, low injection temperature and high displacement are suggested in the application in order to make a longer proppant bed. Besides, the density of SC-CO 2 is relatively high in the formation of low rock porosity which will make the fracturing more effective.The results obtained in this paper will provide reference for SC-CO 2 fracturing design which could promote the development of this technology.

Three‐dimensional complex fracture propagation simulation: Implications for rapid decline of production capacity

“…In addition, the stress component of the traction–separation model is also affected by the damage variable D during the failure of the CE according towhere refers to the nominal stress vector; represents the stress components predicted by the elastic traction–separation behavior without damage for the current displacement. In this model, a bilinear cohesive law 43,44 is used to describe the relationship between traction force and displacement, as shown in Figure 2. In Equation (), dimensionless D represents the overall damage of the material cohesion unit during fracturing.…”

Theoretical and experimental determination of proppant‐crushing ratio and fracture conductivity with different particle sizes

“…7 Therefore, one of the most urgent tasks in developing oil and gas fields is to "reduce cost and increase efficiency". 8 Proppant-crushing ratio and proppant fracture conductivity are two main indicators of proppant performance, 9,10 as well as being important parameters in proppant selection, 11,12 fracture design, 13,14 and postfracture evaluation. 15,16 Proppant-crushing ratio and fracture conductivity are generally tested by physical experiments, 15,[17][18][19] but physical experiments have limitations: long testing time, high cost, limited testing conditions, and significantly different results from repeated experiments under the same conditions.…”

Study on Proppant Transport in Fractures of Supercritical Carbon Dioxide Fracturing

“…Supercritical carbon dioxide (SC-CO 2 ) fracturing is regarded as a promising means in the development of unconventional oil and natural gas on account of its great advantages of environmental protection and resource-saving . CO 2 with specific pressures and temperatures is injected into the well and reaches the supercritical state (above 7.38 MPa and 304.1 K) at a certain position in the wellbore with the heat transfer with formation rocks, which could result in fracturing the formation and carry proppants into the fractures to form the flow channel of oil and natural gas from the reservoir to the well. , …”

“…Relevant studies indicated that CO 2 fracturing fluid would turn into supercritical state under the effect of heat transfer with formation rock. SC-CO 2 has the advantages of better properties of diffusivity, solubility, flowability, and permeability and having less chemical additives, which make this technology a promising method to develop unconventional resources . However, some imperfections of SC-CO 2 fracturing were exposed in field applications.…”

“…19 CO 2 with specific pressures and temperatures is injected into the well and reaches the supercritical state (above 7.38 MPa and 304.1 K) at a certain position in the wellbore with the heat transfer with formation rocks, which could result in fracturing the formation and carry proppants into the fractures to form the flow channel of oil and natural gas from the reservoir to the well. 6,20 With the development of the shale gas, CO 2 fracturing has been tested in many wells in America, Canada, and China and achieved good performance in the field test. Pure liquid CO 2 fracturing was tested in the shale gas of Lewis and Devonian.…”