Pumping Fluid To Seal A Subterranean Fracture

Abstract

The disclosure teaches a method of sealing fractures in a wellbore wherein the steps comprise pumping a first sealing fluid into a wellbore under pressure, monitoring the hydraulic pressure of the sealing fluid in the wellbore for an indicator of seal initialization, stopping the pumping of fluid into the wellbore, monitoring the hydraulic pressure of the sealing fluid in the wellbore, and pumping a second sealing fluid into the wellbore. The disclosure also includes the method wherein the concentration of sealing materials in the first fluid is greater than the concentration of sealing materials in the second fluid and the method wherein the first sealing fluid contains a higher concentration of larger diameter sealing materials than the second sealing fluid. The disclosure also includes a method wherein the pumping rate change between the first pumping of sealing fluid and the pumping of the second sealing fluid. The first and second sealing fluids can be the same. The sealing materials of a sealing fluid are selected such that some of the sealing materials are larger than an estimated original fracture size.

Description

BACKGROUND[0001]During drilling oil and gas wells, subterranean fractures may be penetrated by a wellbore formed by a drill bit. These pre-existing fractures are called natural fractures. These natural fractures may be of various shapes and sizes and some of them may be in a form of vugs, voids, pores, joints, cracks, faults or caverns. During drilling, drilling fluid is normally pumped through hollow drill pipe to the drill bit and through nozzles on the bit into the wellbore flowing upward through the annulus formed between the wellbore and the drill pipe back to surface. The drilling fluid is to carry drilled cuttings to surface, cool the bit, lubricate the drill pipe, apply hydraulic pressure to the wellbore, etc. After the drilled cuttings are separated from the drilling fluid by devices such as shale shaker screens, the drilling fluid then is pumped down through the hollow drill pipe again. This process is called drilling fluid circulation, which is a normal process of drillin...

AI Technical Summary

Benefits of technology

The invention is a method for sealing fractures in a wellbore using soft sealing materials. The method involves pumping the sealing materials into a fracture while controlling the pressure to prevent the sealing materials from leaking to the surrounding rock matrix or cracks. The soft sealing materials can fit the fractures better and help to initialize a seal. The method also includes using a high pump rate to open the fracture wide and deform the sealing materials, assisting in the build-up of fluid pressure in the wellbore. The shut-down period is preferred to be 5 to 20 minutes to allow enough sealing materials to accumulate and enhance the seal. The invention provides a better seal and wellbore strength.

Problems solved by technology

When pump is shut down, fluid in a fracture may leak into the rock matrix, cracks or flow away down the fracture causing the pressure to decrease naturally over time.