Method and process for extracting shale oil and gas by fracturing and chemical retorting in oil shale in-situ vertical well

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.

1 . A method for extracting shale oil and gas by fracturing and chemical retorting oil shale in in-situ vertical well, the method comprising:
 drilling a fractured burning well and several export production wells from the ground to an 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 comprising air, water and a gap filler 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 the gap filler, so as to establish oil gas passages;   establishing a burning chamber within the fractured burning well by injecting a combustible gas and a combustion-supporting gas into the burning chamber, and igniting the combustible gas so that the combustible gas burns 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 thereby achieving extraction of the shale oil and gas by underground in-situ continuous retorting of the oil shale.   
     
     
         2 . A process for implementing the method of extracting shale oil and gas by fracturing and chemical retorting oil shale in in-situ vertical well according to  claim 1 , the process comprising the following steps of:
 1) selecting specific locations of a fractured burning well and export production wells and 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 does not penetrate through the oil shale stratum, wherein the export production wells penetrate through the oil shale stratum, and wherein 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 a gap filler, 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 produce a sufficient pressure difference to implement hydraulic jet perforation; 
 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; 
 iv). 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 sand-containing 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 until 0.5 meter below the oil shale stratum, and, closing the casing and the shale wall gaps by means of an expansion agent; 
 iii). introducing 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 liquid petroleum gas (LPG) and air into the burning chamber via a combustible gas delivery pipe, and, igniting the combustible gas by the electronic ignition system; and 
 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 the shale oil and gas to a ground gas-liquid separator via oil gas passages and the export production wells. 
   
     
     
         3 . A hydraulic casing nozzle, comprising 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 in communication with the casing by a nipple and the other end in communication with the screen pipe by the check valve, wherein an outside of the nipple is cased with the upper centralizer, wherein a pipe wall of the screen pipe is uniformly distributed with several screen meshes, wherein the lower centralizer is cased over the screen pipe, and wherein the guide shoe is secured to a top of the screen pipe. 
     
     
         4 . The method of  claim 1 , wherein the gap filler is quartz sand. 
     
     
         5 . The method of  claim 1 , further comprising:
 introducing in the oil shale stratum an oxidant through the vertical well, to oxidize a sphaltenes and fixed carbon remaining in the oil shale after being retorted.   
     
     
         6 . The method of  claim 1 , where the heat generated is used as a heat source for subsequent retorting. 
     
     
         7 . The method of  claim 1 , further comprising separating the exported shale oil and gas by a ground gas-liquid separator. 
     
     
         8 . The method of  claim 7 , further comprising delivering the separated shale oil to a product tank for storage and sale. 
     
     
         9 . The method of  claim 1  further comprising delivering combustible gas to a gas power package for power generation. 
     
     
         10 . The process of  claim 2 , wherein the gap filler is quartz sand. 
     
     
         11 . The process of  claim 2 , further comprising continuing to inject highly pressurized air into the well, to oxidize sphaltenes and fixed carbon remaining 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. 
     
     
         12 . The process of  claim 2 , further comprising separating the exported shale oil and gas by the ground gas-liquid separator. 
     
     
         13 . The process of  claim 12 , further comprising delivering the separated shale oil to a product tank for storage. 
     
     
         14 . The process of  claim 13 , further comprising delivering the separated combustible gas, via the gas-liquid separator, to a gas power package for power generation.