Apparatus and method for in-situ permeability enhancement of reservoir rock

Abstract

A method of in-situ rock permeability enhancement involves penetration of a target formation by a well, downhole injection of a fluid, action on the fluid by static pressure and shock waves of a specific pattern transmitted downhole along a fluid waveguide and directed to the target formation from a wave reflector, thereby generating dilatant decompaction of the rock. The action on the fluid by static pressure and by shock waves occurs simultaneously, so that static pressure exceeds the capillary pressure in pores of the most common size in the decompacting rock by no less than 1.3 times. The selected shock wave amplitude is equal to or greater than the compressive or tensile stress necessary for dilatant decompaction of the rock. The proposed technical solution will make it possible to improve the efficiency of the in-situ permeability enhancement and rock decompaction process while reducing energy consumption and operating costs.

What is claimed is: 
     
         1 . An apparatus for in-situ permeability enhancement of reservoir rock, comprising:
 a wave generator operably connected to a coniform adapter;   an emitter housing having a first end attached to the wave generator and surrounding the coniform adapter; and   a moveable bearing and fluid tube fluidly connected to a second end of the emitter housing, wherein the emitter housing and fluid tube define a fluid channel.   
     
     
         2 . The apparatus of  claim 1 , wherein the emitter housing comprises a hollow conoid body hermetically sealed to a hollow frustum body at their widest points. 
     
     
         3 . The apparatus of  claim 1 , wherein an emitter section is configured as decreasing along a longitudinal axis of the fluid channel according to the following formula:
     F   H0 =( p   H   a   H   F   H   +p   K   a   K   F   K )/( p   H0   a   H0 )   where:   F H0 —is a zero section of the fluid channel;   p H0 —is process fluid density in the zero section;   a H0 —is wave velocity in the process fluid in the zero section;   F H —is a current section of the fluid channel;   p H —is process fluid density in the current section;   a H —is wave velocity in the process fluid in the current section;   F K —is an estimated section of the fluid channel according to a length of the fluid channel;   p K —is process fluid density in the estimated section; and   a K —is wave velocity in the estimated section.   
     
     
         4 . The apparatus of  claim 1 , further comprising a coniform well wave reflector disposed in a wellbore proximate to a mineral stratum in the reservoir rock and associated with the fluid channel. 
     
     
         5 . The apparatus of  claim 4 , wherein the coniform well wave reflector has a height that is not less than ¼ of a wavelength generated by the emitter. 
     
     
         6 . The apparatus of  claim 4 , wherein a fluid waveguide cross-section changes towards a bottom of the wellbore according to the following formula:
     F   *o =( p   *   a   *   F   *   +p   M   a   M   F   M )/ p   *o   a   *o ,   where:   F *o  is the initial fluid waveguide cross-section;   p *o  is the initial process fluid density;   a *o  is the initial wave velocity in the process fluid;   F *  is the current fluid waveguide cross-section;   p *  is the current process fluid density;   a *  is the current wave velocity in the process fluid;   F M  is the cross-section of the rock mass impacted by the wave;   p M  is the density of the rock mass; and   a M  is the wave velocity in the rock mass.   
     
     
         7 . A method for in-situ permeability enhancement of reservoir rock, comprising the steps of:
 providing a wave generating system having a wave generator operably connected to a coniform adapter, an emitter housing having a first end attached to the wave generator and surrounding the coniform adapter, a moveable bearing and fluid tube fluidly connected to a second end of the emitter housing, and a well wave reflector disposed in a wellbore in fluid communication with the fluid tube;   filling the emitter housing, fluid tube, and wellbore with a process fluid;   generating an energy wave in the process fluid via the wave generator and coniform adaptor; and   redirecting the energy wave from the wellbore into a mineral stratum in the reservoir rock proximate to the wellbore.   
     
     
         8 . The method of  claim 7 , wherein the energy wave is at a wavelength commensurate with a thickness of the mineral stratum, while a processing time is determined based on a specified length of a fracture being created in the mineral stratum, according to the following formula:
     L≥λ=T·a≥ΔÍ·n      Where:   L is the thickness of the target formation;   λ is the wavelength;   T is the wave processing time;   a is the wave velocity;   Δ Í is the increase in fracture length per wave passage; and   N is the number of wave passages needed to achieve the specified fracture length.   
     
     
         9 . The method of  claim 7 , wherein the energy wave is in alignment with areas of cross-section change so that acoustic impedances of wave guides are in equilibrium, according to the following formula:
     F   *o   p   *o   a   *o   =p   *   a   *   F   *   +p   M   a   M   F   M      where:   F *o  is the initial cross-section of a fluid waveguide;   p *o  is the initial process fluid density;   a *o  is the initial wave velocity in the process fluid;   p *  is the current process fluid density;   a *  is the current wave velocity in the process fluid;   F *  is the current fluid waveguide cross-section;   F M  is the cross-section of the rock mass impacted by the wave;   p M  is the density of the rock mass;   a M  is the wave velocity in the rock mass.   
     
     
         10 . The method of  claim 7 , wherein the energy wave simultaneously transfers both static pressure and shock waves such that: the static pressure exceeds capillary pressure in pores of the most common size in the reservoir rock by no less than 1.3 times; and the shock wave amplitude is equal to or greater than the compressive or tensile stress necessary for dilatant decompaction of the reservoir rock.