Injection Wells

Abstract

A method for providing a well injection program in which injection testing is performed on an appraisal well. An appraisal well is selected, downhole sensors are located in the well to measure pressure and temperature, water is injected into the well in a series of step rate tests or injection cycles, the data is modelled to determine a thermal stress characteristic of the well and by reservoir modelling the optimum injection parameters are determined for the well injection program to provide for maximum recovery. This overcomes the need for making thermal stress characteristic measurements on core samples.

1 . A method for a well injection program, comprising the steps:
 (a) selecting an appraisal well;   (b) selecting a perforation interval and length;   (c) locating at least one downhole sensor to measure pressure in the well;   (d) injecting a fluid into the well;   (e) varying the flow rate of injected fluid;   (f) measuring the pressure with flow rate variations to provide measured data;   (g) fitting a first model to the measured data to estimate a thermal stress characteristic of the well;   (h) inputting the thermal stress characteristic into a second model; and   (i) determining injection parameters from the second model.   
     
     
         2 . The method according to  claim 1  wherein the method includes the steps of performing a series of step rate tests and measuring fracture pressure. 
     
     
         3 . The method according to  claim 1  wherein the method includes the steps of performing injection cycling and fall-off analysis. 
     
     
         4 . The method according to  claim 1  wherein the first model describes the development of the thermal stresses around the well on the measured data to estimate a thermal stress characteristic. 
     
     
         5 . The method according to  claim 1  wherein the thermal stress characteristic is a thermal stress parameter. 
     
     
         6 . The method according to  claim 1  wherein the second model is a reservoir model. 
     
     
         7 . The method according to  claim 1  wherein the second model is a hydraulic fracture model. 
     
     
         8 . The method according to  claim 1  wherein the at least one downhole sensor also measures temperature. 
     
     
         9 . The method according to  claim 1  wherein the downhole sensors data sampling rate is 1 Hz or greater. 
     
     
         10 . (canceled) 
     
     
         11 . The method according to  claim 1  wherein the downhole sensors transmit data to the surface via a cable. 
     
     
         12 . The method according to  claim 1  wherein the downhole sensors transmit data to the surface by telemetry. 
     
     
         13 . The method according to  claim 1  wherein the downhole sensors include memory gauges on which the measured data is stored. 
     
     
         14 . The method according to  claim 1  wherein the method includes the step of measuring pressure for different temperatures of injected fluid. 
     
     
         15 . The method according to  claim 1  wherein pressure, temperature and flow rate are measured at the surface of the well. 
     
     
         16 . The method according to  claim 1  wherein the method includes the step of measuring the pressure and flow rate during a first injection cycle and determining fracturing has occurred. 
     
     
         17 . The method according to  claim 16  wherein parameters for the second injection cycle are determined from the first injection cycle. 
     
     
         18 . The method according to  claim 17  wherein the step is repeated for further injection cycles. 
     
     
         19 . (canceled) 
     
     
         20 . The method according to  claim 19  wherein the injected fluid is selected from a group comprising: drill water, filtered seawater or unfiltered seawater. 
     
     
         21 . (canceled) 
     
     
         22 . (canceled) 
     
     
         23 . (canceled) 
     
     
         24 . (canceled) 
     
     
         25 . (canceled) 
     
     
         26 . The method according to  claim 1  wherein the well injection parameters are selected from a group comprising: injection fluid temperature, fluid pump rate, fluid pump duration and fluid injection volume. 
     
     
         27 . The method according to  claim 1  wherein the method includes the further step of carrying out well injection using the well injection parameters.