Determining a property of a formation material

Abstract

Method for determining a property of a formation material in the course of a jet drilling operation, wherein a fluid jet is blasted with erosive power into impingement with the formation material, the method comprising postulating a relationship between the erosive power and a removal rate of formation material as a result of the impingement of the fluid jet with the erosive power on said formation material, the relationship comprising a parameter related to at least one property of the formation material; determining removal rates of formation material for at least two settings of erosive power; and determining the at least one property of the formation material from the relationship and the determined removal rates in dependence on erosive power.

1 . Method for determining a property of a formation material in the course of a jet drilling operation, wherein a fluid jet is blasted with erosive power into impingement with the formation material, the method comprising the steps of:
 postulating a relationship between the erosive power and a removal rate of formation material as a result of the impingement of the fluid jet with the erosive power on said formation material, the relationship comprising a parameter related to at least one property of the formation material;   determining removal rates of formation material for at least two settings of erosive power; and   determining the at least one property of the formation material from the relationship and the determined removal rates in dependence on erosive power.   
     
     
         2 . The method according to  claim 1 , wherein the fluid jet is an abrasive fluid jet comprising abrasive particles. 
     
     
         3 . The method according to  claim 2 , wherein the concentration of abrasive particles in the fluid jet is different between the at least two settings of erosive power. 
     
     
         4 . The method according to  claim 1  wherein at least one of a fluid pressure, pressure drop over a jet nozzle, or velocity of jetted fluid, is different between the at least two settings of erosive power. 
     
     
         5 . The method according to  claim 1  wherein the at least one property comprises a classification of hardness of the formation material. 
     
     
         6 . The method according to  claim 1  wherein the at least one property comprises a rock type. 
     
     
         7 . The method according to  claim 1  wherein the at least one property comprises a porosity. 
     
     
         8 . The method according to  claim 1  wherein the at least one property comprises a permeability. 
     
     
         9 . The method according to  claim 1  wherein the at least one property comprises a tensile strength. 
     
     
         10 . The method according to  claim 1  wherein the relationship includes the erosive power of hydraulic liquid and the erosive power of abrasive particles, and wherein the at least two settings of erosive power are selected such that the effect of changing only erosive power of hydraulic liquid and/or only erosive power of abrasive particles can be determined individually. 
     
     
         11 . The method according to  claim 1  wherein at least one of a threshold pressure and an increase of removal rate per increase of hydraulic pressure above a threshold pressure is determined for hydraulic liquid jetting. 
     
     
         12 . The method according to  claim 1  wherein an increase of removal rate per increase of kinetic energy of abrasive particles is determined for abrasive jetting. 
     
     
         13 . The method according to  claim 1  wherein the at least one property of the formation material is a property that is independent of a drilling or excavation method used for accessing the formation material. 
     
     
         14 . The method according to  claim 1  wherein the at least one property of the formation material is a material property characteristic for the formation material independent of the position of the formation material in an earth formation.