Methods and apparatus for well productivity

Abstract

A system and method for drilling a formation and a method for computing expected production from a wellbore in a formation and/or hydrocarbon reserves associated with the formation, the formation having a plurality of naturally-occurring fractures, the method including computationally modelling the formation; computing one or more wellbore positions intersecting some or all of the fractures; and computing an expected production from the wellbore at least partially based on an expected wellbore damage associated with a particular type of drilling technique.

1 . A method for computing expected production from a wellbore in a formation and/or hydrocarbon reserves associated with a formation, the formation having a plurality of naturally-occurring fractures, the method comprising:
 computationally modelling the formation;   computing one or more wellbore positions intersecting some or all of the fractures;   computing an expected production from the wellbore and/or reserves at least partially based on an expected wellbore damage associated with a particular type of drilling technique.   
     
     
         2 . The method of  claim 1 ; wherein the one or more wellbore positions are computed using and/or based on the model of the formation; and/or the computed expected production of the wellbore is for the wellbore in the one or more wellbore positions. 
     
     
         3 . The method of  claim 1  or  claim 2 , wherein:
 the expected production and/or reserves is/are at least partially based on the inflow from the naturally-occurring fractures; and/or 
 the formation comprises a plurality of micro-fractures between the naturally-occurring fractures and the expected production and/or reserves is/are at least partially based on the inflow from naturally-occurring fractures together with inflow from micro-fractures. 
 
     
     
         4 . The method according to any preceding claim, wherein the method comprises subsequently deciding to drill and produce from a wellbore based on the expected production and/or reserves. 
     
     
         5 . The method according to any preceding claim, wherein the method comprises subsequently deciding to alter the initially-computed wellbore positions based on the expected production and/or reserves. 
     
     
         6 . The method according to any preceding claim, wherein the method comprises determining the need to fracture a near-wellbore formation surrounding the wellbore based on the expected production. 
     
     
         7 . The method according to any preceding claim, wherein the method comprises re-computing one or more of the wellbore positions, intersecting some or all of the fractures, in order to reduce, or eliminate, the need for hydraulic or chemical fracturing. 
     
     
         8 . The method according to  claim 7 , wherein the method comprises computing one or more of the wellbore positions in order to provide a particular or maximum recovery from the formation, without hydraulic or chemical fracturing. 
     
     
         9 . The method according to any preceding claim, wherein the particular technique is or comprises reverse-circulation drilling. 
     
     
         10 . The method according to any preceding claim, wherein the method comprises obtaining data, such as core data, from appraisal wells drilled specifically using the particular type of drilling technique for the purposes of modelling the formation. 
     
     
         11 . The method of  claim 10 , wherein the data is reviewed, and the formation potential re-appraised, by computationally modelling the formation using or based on at least some of the data. 
     
     
         12 . A method of forming a wellbore in a formation; the method comprising:
 using or determining parameters associated with a formation;   computationally modelling the formation using the parameters;   computing one or more wellbore positions, e.g. using the computed model, based on the type of drilling to be used for the formation; and   drilling one or more of the wellbore positions.   
     
     
         13 . The method according to  claim 12 , the method comprising using data associated with the drilling operation to confirm at least one or each of the parameters associated with the formation and the computed model of the formation. 
     
     
         14 . The method of any of  claim 12  or  13 , comprising the method of any of  claims 1  to  11 , wherein the one or more wellbore positions are wellbore positions associated with a particular, optimum or maximum recovery from the formation. 
     
     
         15 . The method according to any of  claims 12  to  14 , wherein the method includes altering, or modifying, one or more of:
 (i) the determined parameters 
 (ii) the computed model; and 
 (iii) the wellbore positions, 
 
       based on an identified difference between data associated with drilling, and expected data associated with the parameters or model. 
     
     
         16 . The method according to any of  claims 12  to  15 , the method comprising real-time monitoring of data while drilling. 
     
     
         17 . A drilling system comprising:
 reverse-circulation drilling apparatus;   data-acquisition apparatus in communication with the drilling apparatus, the data acquisition apparatus being configured to determine formation parameters when drilling using the drilling apparatus; and   formation-modelling apparatus, in communication with the data acquisition apparatus, and configured to use the determined formation parameters with a simulated model of the formation so as to allow for control of the drilling apparatus based on the simulated model of the formation.   
     
     
         18 . The system according to  claim 17 , wherein the formation modelling apparatus is configured to implement the method of any of  claims 1  to  11  and/or the system is configured to implement the method of any of  claims 12  to  16 . 
     
     
         19 . The system according to  claim 18 , wherein the system is configured for use with low permeability formations, such as shale-rock formations. 
     
     
         20 . The system according to any of  claims 17  to  19 , wherein the drilling apparatus comprises at least one flow control device, the flow control device configured to prevent or inhibit undesired flow of fluids from uncontrollably reaching a surface. 
     
     
         21 . The system according to  claim 20 , wherein the flow control device is configured to regulate the flow of fluids from a formation to the data acquisition apparatus. 
     
     
         22 . The system according to any of the  claim 20  or  21 , wherein the flow control device permits isolation and testing of selected zones in the formation. 
     
     
         23 . The system according to any of the  claims 17  to  22 , wherein the data-acquisition apparatus is configured to sample materials, including liquids, gases and/or cuttings provided during drilling, in order to determine formation parameters. 
     
     
         24 . The system according to  claim 23 , wherein the data-acquisition apparatus is configured to compute or determine the location of natural fractures in the rock formation, based on sampled materials from a well. 
     
     
         25 . A system according to  claim 24 , wherein the data-acquisition apparatus is configured to determine hydrocarbon production, or liberation, at a particular drilling region or location, and wherein a determined relative increase in hydrocarbon production indicates the presence of a natural fracture at that drilling region or location. 
     
     
         26 . A system according to any of  claims 17  to  25 , wherein the data-acquisition apparatus is configured to determine formation parameters in real time and is configured to communicate determined parameters to the formation-modelling apparatus in real time. 
     
     
         27 . A system according to any of  claims 17  to  26 , wherein the formation-modelling apparatus is configured to use computational fluid dynamics using finite volumes to model a formation being drilled. 
     
     
         28 . A system according to any of  claims 17  to  27 , wherein the formation-modelling apparatus is configured to verify, generate and/or revise a simulated model of the formation based on determined formation parameters. 
     
     
         29 . A system according to any of  claims 17  to  28 , wherein the formation modelling apparatus is configured to model wellbore inflow, assuming little or no damage to the formation during to drilling. 
     
     
         30 . A system according to any of  claims 17  to  29 , wherein the system is additionally configured to control the drilling apparatus based on the simulated model of the formation. 
     
     
         31 . A system according to  claim 30 , wherein control comprises one or more of: adjustment to expected trajectory of a drilled wellbore; adjustment to the length of a wellbore; drilling of side branches; deviation of the wellbore, in order to increase natural fracture intersection. 
     
     
         32 . A system according to  claim 30  or  31 , wherein control includes drilling a primary wellbore and drilling one or more secondary wellbores from the primary wellbore, each secondary wellbore being drilled in order to intersect one or more natural fractures in the formation. 
     
     
         33 . A system according to  claim 32 , wherein the one or more secondary wellbores are arranged to maximise a number of natural fractures intersected by the wellbores by optimizing orientation or the secondary wellbore(s) in terms of azimuth and/or deviation angle. 
     
     
         34 . A system according to  claim 32  or  claim 33 , wherein the formation-modelling apparatus is configured to update and/or optimise the model based on core data acquired for the primary and/or secondary well bore(s). 
     
     
         35 . A method of drilling a formation comprising:
 drilling a primary wellbore using reverse-circulation drilling apparatus, and   drilling one or more secondary wellbores from the primary wellbore, each secondary wellbore being drilled in order to intersect one or more natural fractures in the formation.   
     
     
         36 . The method according to  claim 35 , wherein the or each secondary wellbore is drilled using reverse-circulation drilling apparatus. 
     
     
         37 . The method according to  claim 35  or  claim 36 , wherein at least the one or more secondary wellbores are drilled during development of an existing field or wellbore or after an exploration/appraisal of the formation. 
     
     
         38 . The method according to any of  claims 35  to  37 , wherein the one or more secondary wellbores are arranged to maximise a number of natural fractures intersected by the wellbores by optimizing orientation or the secondary wellbore in terms of azimuth and/or deviation angle. 
     
     
         39 . The method according to any of  claims 35  to  38 , comprising permitting the well to flow during drilling of the primary wellbore. 
     
     
         40 . The method according to any of  claims 35  to  39 , comprising permitting the well to flow during drilling of the or each secondary wellbore. 
     
     
         41 . The method according to any of the  claims 35  to  40 , comprising determining well and reservoir potential during drilling by determining hydrocarbon content and/or composition from wellbore inflow during drilling. 
     
     
         42 . The method according to any of the  claims 35  to  41 , comprising isolating one or more of the secondary wellbores from the primary wellbore during drilling, wherein such isolation is provided mechanically and/or chemically. 
     
     
         43 . The method according to any of the  claims 35  to  42  comprising determining the location of natural fractures in rock formation, based on sampled materials from a well, in order to determine desired location(s) for secondary wellbores. 
     
     
         44 . The method according to  claim 43 , comprising determining hydrocarbon production, or liberation, at a particular drilling region or location in order to determine the location of natural fractures in order to determine desired location for secondary wellbores. 
     
     
         45 . The method according to  claim 44 , wherein a determined relative increase in hydrocarbon production during drilling indicates the presence of a natural fracture at that drilling region or location. 
     
     
         46 . The method according to any of the  claims 35  to  45 , comprising acquiring data from drilling in order to determine formation parameters, and using the formation parameters with a simulated model of the formation so as to allow for control of the drilling apparatus based on the simulated model of the formation. 
     
     
         47 . The method according to  claim 46 , wherein the formation parameters are used to verify, generate and/or revise the simulated model of the formation. 
     
     
         48 . The method according to any of the  claims 35  to  47 , wherein the method is used in shale-rock formation. 
     
     
         49 . The method according to any of  claims 35  to  48 , comprising acquiring core data for the primary and/or secondary well bore(s) to collect data for the formation in which the natural fractures and hydrocarbons are present and optionally updating the simulated model based on the data and/or core data. 
     
     
         50 . An unconventional hydrocarbon reservoir comprising:
 a primary wellbore having been drilled using reverse-circulation drilling apparatus, and   one or more secondary wellbores having been drilled from the primary wellbore, the or each secondary wellbore intersecting one or more natural fractures in the formation.   
     
     
         51 . The unconventional hydrocarbon reservoir according to  claim 50 , wherein the unconventional hydrocarbon reservoir is or comprises or is comprised in a shale rock formation.