Patent EA-014301-B1 (EA)
Title: Method and apparatus for slurry and operation design in cuttings re-injection
Inventor: GUO QUANXIN
IPC: E21B21/06
Filed: 2006-03-07
Abstract: A method of injecting a slurry in a wellbore, comprising the following stages: defining initial parameters comprising at least one selected from the group consisting of wellbore design parameters which characterize, as well as, wellbore trajectory, parameters , as well as friction parameters of tubing and casing, , parameters characterizing injection zone properties, slurry composition and properties, and injection schedule; defining a mass balance equation for a solids bed; defining a mass balance equation for a suspension solids; segmenting the wellbore into a plurality of elements, wherein each element comprises a plurality of nodes; segmenting a simulation into a plurality of tune intervals; simulating a cuttings re-injection based on the initial parameters for each of the plurality of time intervals by solving the mass balance equation for the solids bed and solving the mass balance equation for the suspension solids for each of the plurality of nodes; obtaining a simulation result by determining at least one optimized parameter from the group consisting of operating parameters, wellbore design parameters, and slurry design parameters and injecting the slurry into a wellbore according to the simulation result.A method for optimizing cuttings re-injection process, comprising the following stages: selecting at least one wellbore design parameter from a group consisting of a wellbore depth, a wellbore diameter, a tubing parameters, a casing parameters, a depth of a top of a perforated interval of the wellbore, a depth of a bottom of a perforated interval of the wellbore, and a deviation angle of the wellbore; selecting at least one operating parameter for the cuttings re-injection from a cuttings re-injection pump rate or a shut-in time; selecting parameters of a slurry to be injected into the wellbore from at least parameters characterizing slurry rheology and size of particles in the slurry; segmenting the wellbore into a plurality of elements, wherein each element comprises a plurality of nodes; performing a simulation at a current time interval, wherein performing the simulation comprises: updating a solid accumulation at a bottom of the wellbore at the current time interval; and performing for each of the plurality of nodes, the following, using the at least one wellbore design parameter, the at least one operating parameter, and the slurry parameters, until the wellbore reaches a steady-state condition for the current time interval: calculating a sliding bed velocity; calculating a suspension cross-section area using the sliding bed velocity; calculating an average suspension concentration using the suspension cross-section area; calculating a solid particle velocity using the average suspension velocity and calculating a solid volume concentration in suspension using the solid particle velocity; obtaining an optimized simulation result based on the simulation of the input parameters after the steady-state condition is reached, wherein the obtaining optimized simulation result comprises determining at least one optimized parameter selected from the group consisting of operating parameters, wellbore design parameters, and slurry parameters; and injecting a slurry into a wellbore according to the optimized simulation result.