Abstract:
The present invention provides a method and a process for extracting shale oil and gas by fracturing and chemical retorting oil shale in in-situ vertical well. A vertical well ( 1 ) is drilled towards an underground oil shale stratum ( 6 ) and a highly pressurized medium is injected into the oil shale stratum. Cracks of 1 to 3 mm are fractured out in the oil shale stratum with the well serving as a center and are filed with gap fillers, so that oil gas passages ( 8 ) are established. Then, a heating apparatus is added into the oil shale stratum to heat the oil shale stratum to 550° C., the oil shale is initially retorted, the shale oil and gas are extracted, and the shale oil and gas are led out of the ground via the oil and gas channel. After that, an oxidizer is introduced for oxidization reaction with a sphaltenes and fixed carbon contained in the oil shale after being retorted, where the heat generated is used as a heat source for subsequent retorting, thus achieving underground in-situ shale oil extraction. This solves the problem that existing ground-level retorting has in terms of large recovery costs, difficult treatment of tailings, a variety of environmental issues, and large land-use footprint.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention discloses a method and a process for extracting shale oil and gas by fracturing and chemical retorting oil shale in in-situ vertical well, in which shale oil is extracted in in-situ underground oil shale and is served as unconventional oil and gas energy for making up shortage of petroleum resources, and which belong to a technical field of retorting of petroleum. 
         [0003]    2. Description of the Related Art 
         [0004]    At present, shale oil (artificial petroleum), which is used to substitute for naturally occurring petroleum, may be refined from shale oil by virtue of retorting technology, and is also used for electricity generation by utilizing combustion thereof. Under the current situation that price of the oil keeps high, shale oil refining has good economic benefits and is a most realistic available measure to make up shortage of naturally occurring petroleum. Electricity generation by oil shale has good economic, environmental and social benefits to these provinces and districts which encounter shortage of coals. However, production and development of shale oil always adopts conventional method of underground exploitation and on-ground retorting, which encounters lots of shortcomings
       1). The on-ground retorting has large excavation cost.   2). The on-ground retorting needs large land-use footprint.   3). The on-ground retorting leads to a great deal of landslide in exploration area.   4). The tailings resulted from the on-ground retorting are difficult to be treated, and its bulk accumulation causes secondary pollution.   5). The tailings resulted from the on-ground retorting carry away lots of heat so that heat from the tailings is unavailable, which results in energy waste.   6). Waste gas and sewage obtained from the on-ground retorting causes excessive pollution of the environment.       
 
       SUMMARY 
       [0011]    The present invention discloses a method and a process for extracting shale oil and gas by fracturing and chemical retorting oil shale in in-situ vertical well, which fundamentally solve the above mentioned shortcomings and problems caused by underground exploitation and on-ground retorting. 
         [0012]    The following is a technical solution of a method for extracting shale oil and gas by fracturing and chemical retorting oil shale in in-situ vertical well disclosed in the present invention. 
         [0000]    The method comprises:
       drilling, depending on the situation of an oil shale stratum, a fractured burning well and several export production wells from the ground to the underground oil shale stratum, wherein the export production wells are distributed in a honeycombed manner around the fractured burning well as a center; establishing a fracturing chamber within the fractured burning well, to pressurizedly fracture out the oil shale stratum; injecting a highly pressurized medium for the oil shale stratum (air, water and quartz sand) into the fractured burning well, and fracturing out several cracks of 1 to 3 mm in the oil shale stratum, the cracks being filled with gap fillers (quartz sand), so as to establish oil gas passages; establishing a burning chamber within the fractured burning well, injecting a combustible gas and a combustion-supporting gas into the burning chamber, and, igniting the combustible gas so that the combustible gas is burning at a bottom of the burning chamber (to ignite combustible matter in the oil shale), to heat the oil shale stratum up to 550-600° C., to achieve heating and retorting of the oil shale so that the shale oil and gas are driven and extracted; exporting the shale oil and gas to the ground through the oil gas passage and the export production wells; introducing, in the oil shale stratum, an oxidant through the vertical well, to oxidize a sphaltenes and fixed carbon remained in the oil shale after being retorted, where the heat generated is used as a heat source for subsequent retorting, thereby achieving extraction of the shale oil and gas by underground in-situ continuous retorting of the oil shale; separating the exported shale oil and gas by a ground gas-liquid separator, and delivering the separated shale oil to a product tank for storage and sale; and, delivering combustible gas to a gas power package for power generation.       
 
         [0014]    A process for implementing the mentioned method of extracting shale oil and gas by fracturing and chemical retorting oil shale in in-situ vertical well according to the present invention is disclosed. The process comprising the following steps of:
       1). depending on distribution and strike of an oil shale stratum, selecting specific locations of a fractured burning well and export production wells, drilling a fractured burning well and several export production wells from the ground to the underground oil shale stratum, wherein a drilling depth of the fractured burning well should not penetrate through the oil shale stratum, the export production wells should penetrate through the oil shale stratum, and, the export production wells are distributed in a honeycombed manner around the fractured burning well as a center;   2). establishing a fracturing chamber within the fractured burning well, taking out a well casing, injecting a highly pressurized medium in to the oil shale stratum through the fractured burning well, pressurizedly fracturing out several cracks of 1 to 3 mm in the oil shale stratum, and filling the cracks with gap fillers (quartz sand), so as to establish oil gas passages; wherein the step 2) further comprises:
           i). drifting and flushing the well;   ii). running a hydraulic casing nozzle into a wellbore;   iii). closing the casing and shale wall gaps to form a closed fracturing space;   iv). implementing a hydraulic jet perforation, by the hydraulic casing nozzle, on the oil shale stratum, wherein a mortar containing base fluid (water) and sand-laden fluid at 20-35% is pumped at a cutting stage, and, when the sand-laden fluid is distanced from the nozzle at about 25 meters, pump speed is sharply increased to ensure that a sufficient pressure different (55-80 MPa) which is required to implement the hydraulic jet perforation is obtained;   v). replacing fracture rocks from the perforation, after 2-3 minutes of operation of the hydraulic jet perforation;   vi). pumping crosslinked carbamidine gel and sand (at a rate of 20-30: 40-60), to enhance an expansion strength;   vii). discharging fluid after fracturing, and flushing the sand to support the cracks;   viii). injecting a fluid temporary plugging agent into the wellbore;   vi). lifting up a drilling tool to a designed position, to fracture a next stratum, and repeating the steps iii). to vi).;   
           3). establishing a burning chamber within the fractured burning well; wherein the step 3) further comprises:
           i). flushing the well, to bring the sand-contained water within the fractured burning well onto the ground;   ii). equipping a sealing casing onto a head of the fractured burning well and running the sealing casing till 0.5 meter under the oil shale stratum, and, closing the casing and the shale wall gaps by means of an expansion agent;   iii). Equipping combustible gas and air introducing pipes and an electronic ignition system within the fractured burning well, and, closing the head, to form a burning chamber in a segment of the oil shale stratum;   iv). delivering LPG and air into the burning chamber via a combustible gas delivery pipe, and, igniting the combustible gas by the electronic ignition system;   v). heating the oil shale stratum to 550-600° C. after igniting the oil shale, stopping supply of the combustible gas when it is measured that temperature of the gas from the production well reaches 200° C. and, driving and extracting some of the shale oil and gas to a ground gas-liquid separator via oil gas passages and the export production wells;   
           4). continuing to inject highly pressurized air into the well, to oxidize a sphaltenes and fixed carbon remained in the oil shale after being retorted, under high temperature, so as to generate fresh combustible gas while driving and extracting the shale oil and gas to the ground via the oil gas passages and the export production well;   5). separating the exported shale oil and gas by the ground gas-liquid separator, and delivering the separated shale oil to a product tank for storage; and,   6). delivering the separated combustible gas, via the gas-liquid separator, to a gas power package for power generation.       
 
         [0035]    There are six export production wells distributed in a honeycombed manner. 
         [0036]    The highly pressurized medium is selected from air, water or mortar. 
         [0037]    The oxidant is selected from air or oxygen-enriched gas. 
         [0038]    The hydraulic casing nozzle mainly comprises an upper centralizer, an ejection gun, a check valve, a lower centralizer, a screen pipe and a guide shoe, wherein a surface of the ejection gun is provided with an ejection nozzle, the ejection nozzle has one end communicated with the casing by a nipple and the other end communicated with the screen pipe by the check valve, an outside of the nipple is cased with the upper centralizer, pipe wall of the screen pipe is uniformly distributed with several screen meshes, the lower centralizer is cased over the screen pipe, and, the guide shoe is secured to a top of the screen pipe. 
         [0039]    The present invention has the following positive effects. 
         [0040]    The shale oil is extracted in in-situ underground oil shale by a chemical heat treatment process of fracturing and chemical retorting the shale oil and gas, which avoids bulk exploitation of oil shale mine and averts environmental pollution brought by on-ground retorting. Secondly, underground continuous retorting is achieved by utilizing a sphaltenes and fixed carbon remained in the oil shale after being retorted, accordingly, the heat is self-sufficient. Thirdly, the chemical heat treatment process is neither a single physical heating process nor an underground spontaneous combustion process, pores in the rock are gradually increased during the course of reaction, and, it is suitable for most oil shale strata. The present invention has advantages of small investments, low operating costs, small environmental pollutions, high resource utilization rate, and fast yields of oil and gas, etc.. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]      FIG. 1  is a principle diagram of a method for extracting shale oil and gas by fracturing and chemical retorting oil shale in in-situ vertical well according to the present invention; 
           [0042]      FIG. 2  is a structural schematic diagram of distribution of vertical wells according to the present invention; and 
           [0043]      FIG. 3  is a structural principle diagram of a hydraulic casing nozzle according to the present invention; 
       
    
    
       [0044]    in which: 
         [0045]      1 . fractured burning well,  2 . export production well,  3 . gas-liquid separator,  4 . product tank,  5 . gas power package,  6 . oil shale stratum,  7 . other stratum,  8 . oil gas passage,  9 . material conveyor,  10 . discharge and transport machine,  11 . oil pump,  12 . crack,  13 . fracturing fluid tank,  14 . LPG storage tank,  15 . oxidant tank,  16 . upper centralizer,  17 . ejection gun,  18 . ejection nozzle,  19 . check valve,  20 . lower centralizer,  21 . screen pipe,  22 . guide shoe,  23 . casing, and,  24 . nipple. 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0046]    In order to provide a much clearer understanding of essences and characteristics of the present invention, implementation and positive effects of the present invention will be described hereinafter in detail in conjunction with these embodiments. It should be understood that the below description is not intended to limit the scope of the present invention. 
       Embodiment 1 
       [0047]    Fuyu-Changchun Mountain Oil Shale Mine, in which a total reserves is of 45.274 billion tons, is taken as an implementation base. The oil shale has an average grade of 5.53%, an industrially developable resources total amount of 18 billions, an embedded depth of 160-800 meters with top and bottom strata of mousey shale, and an average thickness of 5 meters. 
         [0048]    As shown in  FIG. 1 , depending on distribution and strike of an oil shale stratum, specific locations of a fractured burning well and export production wells are selected, a fractured burning well  1  (a head of which has a diameter of 200 mm) and six export production wells  2  (a head of each of which has a diameter of 200 mm) are drilled from a underground rock stratum  7  to a underground oil shale stratum  6  (which is distanced from the ground at 380 meters). As shown in  FIG. 2 , the six export production wells  2  are distributed in a honeycombed manner around the fractured burning well  1  as a center. The fractured burning well and the export production wells are drilled from the ground to the underground oil shale stratum, wherein a drilling depth of the fractured burning well should not penetrate through the oil shale stratum, the export production wells should penetrate through the oil shale stratum, and, the export production wells are distributed in a honeycombed manner around the fractured burning well as a center.
       2). A fracturing chamber is established within the fractured burning well, a well casing is taken out, a highly pressurized medium is injected into the oil shale stratum through the fractured burning well, several cracks of 1 to 3 mm are pressurizedly fractured out in the oil shale stratum, and the cracks are filled with gap fillers (quartz sand), so as to establish oil gas passages. The step 2) further comprises:
           i). drifting and flushing the well;   ii). running a hydraulic casing nozzle into a wellbore;   iii). closing the casing and shale wall gaps to allow the oil shale stratum to form a closed fracturing space;   iv). implementing a hydraulic jet perforation, by the hydraulic casing nozzle, on the oil shale stratum  6 , wherein a mortar containing base fluid (water) and sand-laden fluid (at 20-35%) is injected from the fracturing fluid tank  13  into the oil shale stratum  6  by a material conveyor  9  (at a cutting stage), and, when the sand-laden fluid is distanced from the nozzle at about 25 meters, pump speed is sharply increased to ensure that a sufficient pressure different (55-80 MPa) which is required to implement the hydraulic jet perforation is obtained to fracture the oil shale stratum  6  to generate cracks  12  of 1-3 mm;   v). replacing fracture rocks from the perforation, after 2-3 minutes of operation of the hydraulic jet perforation;   vi). pumping carbamidine gel base fluid by an annular bore, in accordance with a design annular bore discharge capacity or at a maximum pump speed allowed by an maximum pressure of annular bore, and, pumping crosslinked gel and sand, in accordance with a design of an oil pipe, (to enhance an expansion strength);   vii). discharging fluid after fracturing, wherein the quartz sand is remained to support the cracks, forming a plurality of oil gas passages  8 , the plurality of oil gas passages  8  being converged and communicated with the export production well  2 ;   viii). injecting a fluid temporary plugging agent into the wellbore;   iv). lifting up a drilling tool to a designed position, to fracture a next stratum, and repeating the steps iii). to vi).   
           3). A fracturing chamber is established within the fractured burning well. The step  3 ) further comprises:
           a first step of, flushing the well, to bring the sand-contained water out of the well onto the ground;   a second step of, equipping a sealing casing onto a head of the fractured burning well and running the sealing casing till 0.5 meter under the oil shale stratum, and, closing the casing and the shale wall gaps by means of an expansion agent;   a third step of, equipping combustible gas and air introducing pipes and an electronic ignition system within the fractured burning well, and, closing the head, to form a burning chamber in a segment of the oil shale stratum;   a fourth step of, delivering LPG and air from a LPG storage tank  14  and an oxidant tank  15  respectively through the fractured burning well  1  into the oil shale stratum  6  by a material conveyor  9 , and, igniting the combustible gas by the electronic ignition system;   a sixth step of, heating the oil shale stratum 6 to 550-600° C. after igniting the oil shale, stopping supply of the combustible gas when it is measured that temperature of the gas from the production well  2  reaches 200° C. and, driving and extracting some of the shale oil and gas to a ground gas-liquid separator  3  via oil gas passages  8  and the export production wells  2 ;   introducing an oxidant into the oil shale stratum  6  to oxidize a sphaltenes and fixed carbon remained in the oil shale after being retorted, where the heat generated is used as a heat source for subsequent retorting the subsequent oil shale progressively, wherein the generated shale oil and gas are passed through;   
           4). continuing to inject highly pressurized air (the air: 1000 m 3  per hour) from the oxidant tank  15  into the fractured burning well  1  by a material conveyor  9 , to oxidize asphaltenes and fixed carbon remained in the oil shale  6  after being retorted, under high temperature, so as to generate fresh combustible gas (while driving the shale oil and gas) to the gas-liquid separator  3  via the oil gas passages  8  and the export production well  2 , so that the underground in-situ extraction of the shale oil and gas is achieved;   5). separating the exported shale oil and gas by the ground gas-liquid separator  3 , and delivering the separated shale oil to a product tank  4  for storage and sale, by an oil pump; and,   6). delivering the separated combustible gas, via the gas-liquid separator  3 , to a gas power package  5  for power generation, by a discharge and transport machine  10 .       
 
       Embodiment 2 
       [0069]    Qiangguo Oil Shale Mine, in which a total mining area is of 675.5 km 2 , the total resources is of 6.172 billion tons and the exploitable total resources is of 4.94 billion tons, is taken as an implementation base. The oil shale has an average grade of 5%, an embedded depth of 160-800 meters with top and bottom strata of mousey shale, and an average thickness of 6 meters. 
         [0070]    As shown in  FIG. 1 , depending on distribution and strike of an oil shale stratum, specific locations of a fractured burning well  1  and export production wells  2  are selected, a fractured burning well  1  (a head of which has a diameter of 200 mm) and six export production wells  2  (a head of each of which has a diameter of 200 mm) are drilled from a underground rock stratum  7  to a underground oil shale stratum  6  (which is distanced from the ground at 380 meters). As shown in  FIG. 2 , the six export production wells  2  are distributed in a honeycombed manner around the fractured burning well  1  as a center. The fractured burning well and the export production wells are drilled from the ground to the underground oil shale stratum, wherein a drilling depth of the fractured burning well should not penetrate through the oil shale stratum, the export production wells should penetrate through the oil shale stratum, and, the export production wells are distributed in a honeycombed manner around the fractured burning well as a center.
       2). A fracturing chamber is established within the fractured burning well, a well casing is taken out, a highly pressurized medium is injected into the oil shale stratum through the fractured burning well, several cracks of 1 to 3 mm are pressurizedly fractured out in the oil shale stratum, and the cracks are filled with gap fillers (quartz sand), so as to establish oil gas passages. The step 2) further comprises:
           i). drifting and flushing the well;   ii). running a hydraulic casing nozzle into a wellbore;   iii). closing the casing and shale wall gaps to allow the oil shale stratum to form a closed fracturing space;   iv). implementing a hydraulic jet perforation, by the hydraulic casing nozzle, on the oil shale stratum  6 , wherein a mortar containing base fluid (water) and sand-laden fluid (at 20-35%) is injected from the fracturing fluid tank  13  into the oil shale stratum  6  by a material conveyor  9  (at a cutting stage), and, when the sand-laden fluid is distanced from the nozzle at about 25 meters, pump speed is sharply increased to ensure that a sufficient pressure different (55-80 MPa) which is required to implement the hydraulic jet perforation is obtained to fracture the oil shale stratum  6  to generate cracks  12  of 1-3 mm;   v). replacing fracture rocks from the perforation, after 2-3 minutes of operation of the hydraulic jet perforation;   vi). pumping carbamidine gel base fluid by an annular bore, in accordance with a design annular bore discharge capacity or at a maximum pump speed allowed by an maximum pressure of annular bore, and, pumping crosslinked gel and sand, in accordance with a design of an oil pipe, (to enhance an expansion strength);   vii). discharging fluid after fracturing, wherein the quartz sand is remained to support the cracks, forming a plurality of oil gas passages  8 , the plurality of oil gas passages  8  being converged and communicated with the export production well  2 ;   viii). injecting a fluid temporary plugging agent into the wellbore;   iv). lifting up a drilling tool to a designed position, to fracture a next stratum, and repeating the steps iii). to vi).   
           3). A fracturing chamber is established within the fractured burning well. The step 3) further comprises:
           a first step of, flushing the well, to bring the sand-contained water out of the well onto the ground;   a second step of, equipping a sealing casing onto a head of the fractured burning well and running the sealing casing till 0.5 meter under the oil shale stratum, and, closing the casing and the shale wall gaps by means of an expansion agent;   a third step of, equipping combustible gas and air introducing pipes and an electronic ignition system within the fractured burning well, and, closing the head, to form a burning chamber in a segment of the oil shale stratum;   a fourth step of, delivering LPG and air from a LPG storage tank  14  and an oxidant tank  15  through the fractured burning well  1  into the oil shale stratum  6  by a material conveyor  9 , and, igniting the combustible gas by the electronic ignition system;   a sixth step of, heating the oil shale stratum  6  to 550-600° C. after igniting the oil shale, stopping supply of the combustible gas when it is measured that temperature of the gas from the production well  2  reaches 200° C. and, driving and extracting some of the shale oil and gas to a ground gas-liquid separator  3  via oil gas passages  8  and the export production wells  2 ;   introducing an oxidant into the oil shale stratum  6  to oxidize a sphaltenes and fixed carbon remained in the oil shale after being retorted, where the heat generated is used as a heat source for subsequent retorting the subsequent oil shale progressively, wherein the generated shale oil and gas are passed through;   
           4). continuing to inject highly pressurized air (the air: 1000 m 3  per hour) from the oxidant tank  15  into the fractured burning well  1  by a material conveyor  9 , to oxidize a sphaltenes and fixed carbon remained in the oil shale  6  after being retorted, under high temperature, so as to generate fresh combustible gas (while driving the shale oil and gas) to the gas-liquid separator  3  via the oil gas passages  8  and the export production well  2 , so that the underground in-situ extraction of the shale oil and gas is achieved;
           separating the exported shale oil and gas by the ground gas-liquid separator  3 , and delivering the separated shale oil to a product tank  4  for storage and sale, by an oil pump; and,   delivering the separated combustible gas, via the gas-liquid separator  3 , to a gas power package  5  for power generation, by a discharge and transport machine  10 .   
               
 
       Embodiment 3 
       [0091]    Referring to  FIG. 3 , there discloses a hydraulic casing nozzle involved in embodiments  1  and  2 , it mainly comprises an upper centralizer  16 , an ejection gun  17 , a check valve  19 , a lower centralizer  20 , a screen pipe  22 , a guide shoe  23 , a casing  23  and a nipple  24 , wherein a surface of the ejection gun  17  is provided with an ejection nozzle  18 , the ejection nozzle  17  has one end communicated with the casing  23  by a nipple  24  and the other end communicated with the screen pipe  21  by the check valve  19 , an outside of the nipple  24  is cased with the upper centralizer  16 , pipe wall of the screen pipe  21  is uniformly distributed with several screen meshes, the lower centralizer  20  is cased over the screen pipe  21 , and, the guide shoe  22  is secured to a top of the screen pipe  21 .