US3465826A - High-temperature water injection - Google Patents

Description

lilih'hb "iihi Eiihliiii; SEARESH iihllllii United States Pat ent 3,465,826 HIGH-TEMPERATURE WATER INJECTION Paul L. Terwilliger, Fox Chapel Borough, Pa., assignor to Gulf Research & Development Company, Pittsburgh,

Pa., acorporation of Delaware 5 quate to introduce the desired amount of heat into the N Drawing, Fil d O t, 19, 1967, S N 676,612 formation, the direction of pressure differential between Int. Cl. E21b 43/24, 43/26 the well and the formation is reversed and the formation US. Cl. 166303 4 Claims fluids produced through the well. In one embodiment of this invention, the water discharged from the heater is substantially saturated and the pressure on the water is ABSTRACT OF THE DISCLOSURE thereafter increased by means of a pump to provide a A method of heating an oil-bearing subsurface forma- Pressure high gh f ffaethfe the fol'matiefl- I tion to increase the rate of flow of oil therefrom in which The Water he lhleeted 1S heated a temperature water at a temperature of 500 to 700 F. is displaced above m a heater caliahle of wlthstehdlhg a P d a 11 d i h f ti at a rate causing 15 sure in excess of the saturat1on pressure of water at the f t i of h f r ati The pressure on the h temperature to wh1ch the water 1s heated. A fired. heater water is maintained at a level which will maintain the Whleh the Water 15 eh'eulated h h 15 P water in the liquid phase while it is in the well. Larger ferred- When'the pfedhehve formehon penetrated y the quantities of heat can be delivered to the formation by well to be stimulated 15 Father Shallow, e p at the hot water at the conditions specified than by steam. a depth of 2,000 feet less, the Water y be P p to the desired pressure for fracturing the formation before being heated to a temperature of 500 F. or higher. Ordinarily a pressure in the range of about 0.6 to 0.85 This lhvehhoh relates. to a method for lhcrehslhg p.s.i. per foot of depth is required to fracture formations. rate of prodhchoh of oh from Wells h more parhch' Water heaters suitable for operation in an oil field and larly to a method for thermal shmhlahoh of Wells penecapable of heating water to the desired temperature and trating underground reservoirs contain ng viscous oils. of withstanding any desirable pressure can be obtained A methhd that h been. used Increasing the rate without difiiculty. Pressures of 5000 p.s.i. cause no diffihf produchoh of oh.wehs 18 9 dlspiace steam .dowh the culty and even higher pressures can be obtained. In conweh and i l h Into the oh'heahhg fhhhahhh' After trast, steam generators suitable for oil field operation are the steam in ect on has continued for a period long limited to a maximum pressure of approximately 2500 enough to increase the temperature of the well and at psi Because of the low density of Steam the pressure least a portion of the underground reservoir, the pressure Supplied by the static head of Steam above the formation within the well is decreased to allow fluids to fiow from is relatively smalL the fohhhhoh mtg the W The hot water is displaced down the well and into the The thermhl shmulahoh by Steam lhlechoh Increases oil-bearing formation at a rate higher than the oil in the the productivity of wells in several ways. The high temformation can flow outwardly through the naturally perature of the h melts Paraihh and the Steam h curring passages in the formation. In this manner, the cohdehsed Water .remove the paraihh and h h deposhed formation is fractured to provide channels capable of shhds from the h The l h heals the oh h the forma- 40 delivering the hot water outwardly into the formation for hoh and thereby-xedhces Its vlscohhy' The 01 1 h q substantial distances from the Well. The rate of injection more readily P h h formahoh when the dhechoh required for fracturing can be readily determined. Before prhssure dlhfehehhal 1S revershdi Large decrhases m a fracture has been created, the rate of displacement of l h h posslhle when the 1h reserve" a liquid into the fracture is substantially proportional to hlgh h hence the method 15 parhchlahy hh the pressure applied to the liquid. After a fracture is h Shmulhhhg pehetrahhg reservohs cohtahhhg created, increases in the rate of injection do not result in vlscouh Addlhohahy the Water Fesulhhg h cohany substantial increase in the pressure. It is desirable to dehsahoh of the Sleam m the fhrmahoh occhplhs a displace the hot water downwardly through tubing in the tion of the space in the formation and thereby increases wen rather than through casing, to decrease loss of heat the phessure m the formahoh' to formations between the productive formation and the It IS hsuahy rehommehded t the dlsplahed ground surface. The actual rate of displacement of hot dowh weh and Into a forhlahoh be superheated to water to fracture the formation will depend on the percrease the amount of heat in each pound of the steam. meabflity and strength of the formation. A rate in the h h i however a process 15 de range of 1 to 20 barrels per minute may be required. The scribed m which a mlxture of steam and waier fracture can be initiated with cold water which is foltaining relatively minor amounts of water 15 dlsplaced lowed y the hot Water- If g flow rates are required down h Weill ahd mto the underground forinauoh' The to initiate fracturing, it may be desirable to bypass the water is mixed with the steam only to provide a means water heater initially g gisphthhg of the sohds or Soluble Salts in the boiler Displacement of heat into formation is continued for 66 W21 er. 0 The thermal stimulation of wells by steam injection is i sgfg ggf a gi 51:2 :2 ig gifiggt gi a h g fg limited to use in relatively shallow formations because fluids sufficiently that the fluids will flow readily to the the high pressure existing in deeper formations cannot be Well on reduction in pressure in Well The length of produced in boilers suitable for use in oil fields. Because time that in.ecfion is continued will debend upon the of the high compressibility of incl-Easing the pre? characteristic s of the oil reservoir such as the thickness igt s e gei ivs i he i e shl f super eated steam ls of the oil sands, the viscosity reduction required for ac. This invention resides in a method for the thermal ceptable P l rateS, the Well spacing, etc. and the stimulation of wells in which water is heated to a temamelmt of h h f deslred- It 15 usually deslrahle perature of at least 500 F. and preferably in the range 70 continue the in ection of hot water for at least two weeks of 550 to 700 F. at a pressure exceeding the saturation pressure of water at the highest temperature attained 3,465,826 Patented Sept. 9, 1969 by the water. The hot water is then displaced down a well and into an oil-bearing formation at a pressure high enough to fracture the formation. After continuing to inject the hot water into the formation for a period adebefore turning the well around and producing formation fluids. Continued injection of hot water for periods as .long as two months before reversing the direction of flow can be used. After injection of the hot water has been completed, the pressure within the Well is reversed to cause flow from the formation into the well. The reversal of flow can follow immediately the injection of hot water, or the well may be shut in for a period to allow dissemination of heat more widely through the formation before flow from the formation to the well is begun.

The method of this invention permits the delivery of heat into subsurface formations at higher rates than are possible by the injection of steam. At temperatures above 500 F., the difference between the enthalpy of saturated steam and saturated water decreases rapidly. The high density of water produces a high static head in the well at the level of injection into the formation that is available to increase the rate of flow of water from the wellhead to the productive formation. The higher density of water also reduces the velocity through the well tubing required for delivery of a given number of pounds of hot fluid into the formation. Although the amount of heat that can be released from a pound of steam is substantially higher than the amount of heat that can be released by a pound of Water, the number of pounds of water that can be de livered into the formation with a given wellhead pressure is enough greater than the number of pounds of steam to allow an increased delivery of heat to the formation by means of the hot water. Because of the higher pressure at which Water heaters can operate as compared to steam generators, a further increase in rate of heat delivery is possible by using higher wellhead pressures for hot Water injection. Moreover, because steam delivered into the formation condenses, the volume of injected fluids in the formation at completion of the heating step is higher when water is used as a heating medium.

The increased rate of delivery of heat possible by hot water as compared with steam is illustrated by the following example.

In a Well penetrating a formation at a depth of 2000 feet, a bottom hole pressure of 2000 p.s.i. is required to fracture the formation. The maximum operating pressure for the steam generator is 2500 p.s.i. The density of steam at 2250 p.s.i. and 652 F. is 6.5 lbs/cu. ft. A column of that steam 2000 feet high has a static head of 6.5/144 2000=90 p.s.i. At a bottom hole pressure of 2000 p.s.i. for the fracturing operation, the pressure drop in the tubing from the wellhead is AP=2500+902000=590 p.s.i.

AP per 100 feet of 1ength=30=C C C V. From the Crane Company Piping Book for 2-inch schedule 40 tubmg Hg==enthalpy of saturated steam at 2500 p.s.i.=1091 Hr=enthalpy of saturated water at reservoir temperature=70 13,000X24 (109l--70)=322 10 B.t.u./day

If hot water (liquid) is displaced down the well into the formation:

The density of water at 2500 p.s.i. and 668 F.=35 lbs/cu. ft.

Static head of the Water=35f144 2000=486 p.s.i.

AP in tubing:2500+486-2000=986 p.s.i.

For an estimated flow rate of 10,000 b./d.:

1 .:MQKM. 24 X 3600 X 0. 785 X4.

=30 ftjsec. 1 '1 *Craft, Holden & Graves; Well Design; Drilling and Production, 1962.

Hw=enthalpy of water at 2500 p.s.i. and 688:730;

11,500 b./d. 350 #/b. (73070)=2660 10 B.t.u./

day

N is Reynolds number d is pipe diameter, inches U is velocity, ft./sec.

p is density, gal.

u is viscosity, cps.

f is friction factor L is length, ft.

As shown by the above calculations, the displacement of hot water allows injection of 2660 10 B.t.u./day into the formation whereas with steam generating equipment capable of operating at the same pressure only 322 10 B.t.u. can be supplied to the formation by the injection of steam. The injection of hot water makes possible further increases in heat injection by pumping the hot water to higher pressures either before delivery to, or after leaving, the heater. Increasing pressure on steam after it is generated is not feasible because of its high compressibility. Injection of the hot water at a rate high enough to fracture the formation minimizes displacement of oil away from the well and causes delivery of heat to portions of the formation remote from the well.

The requirement that the hot water be injected at a rate high enough to cause fracturing will usually insure a pressure in the well high enough to prevent vaporization of the water in the well. If the temperature of the water at the level at which it enters the formation is 500 F., a pressure of 700 p.s.i. is adequate to prevent vaporiza-= tion of the water.

I claim.

1. A method of increasing production of oil from an oil-bearing subsurface formation comprising pumping water down a well and into the oil-bearing formation at a rate causing creation of a fracture in the formation, heating the water to a temperature of 500 to 700 F. before delivery of the water into the well, the pressure on the water being high enough to maintain the water in the liquid phase until it is discharged from the well into the oil-bearing formation, continuing the injection of water into the formation for a period adapted to transfer a desired quantity of heat to the oil-bearing formation, lowering the pressure in the well to a pressure lower than the pressure in the oil-bearing formation, and producing liquids flowing from the formation into the well.

2. A method as set forth in claim 1 in which the well is shut in after completion of the injection of hot water and before commencing production of formation fluids through the well for a period to increase dissemination of heat through the formation.

3. A method of heating an oil-bearing formation penetrated by a well to stimulate flow of oil therefrom come prising displacing water down the well and into the formation at a. rate causing initiation of a fracture in the formation, displacing down the Well water at a temperature in the range of 500 to 700 F. and at a pressure adapted to maintain the water in the liquid phase while in the well at a rate adapted to hold the fracture open, continuing the injection of the hot water at a rate adapted to hold the fracture open for a period adapted to deliver the desired quantity of heat to the formation, reducing the pressure in the well to a pressure lower than the pressure in the formation, and producing fluids flowing from the formation into the well.

4. A method of heating an oil-beaming formation penetrated by a well to stimulate flow of oil therefrom comprising displacing unheated water down the well and into the formation causing initiation of a fracture in the formation, displacing down the well and into the fracture to deliver the desired quantity of heat into the formation, shutting in the well for a period to disseminate heat through the formation, reducing the pressure in the well to a pressure lower than the pressure in the formation, and producing fluids flowing from the formation into the well.

References Cited UNITED STATES PATENTS 1,237,139 8/1917 Yeomans 166-11 3,042,114 7/1962 Willman 166-11 3,125,072 3/1964 Brandt et al.

3,167,120 1/1965 Pryor 166-11 X 3,284,281 11/1966 Thomas 166-40 X 3,288,214 ll/1966 Winkler 166-40 3,330,353 7/1967 Flohr 166-40 STEPHEN I. NOVOSAD, Primary Examiner U.S. cll X.R,