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Test Method to Quantify Spacer Efficacy in Cleaning Filter Cake and Study its Effects on Cement Bond Quality

IP.com Disclosure Number: IPCOM000227589D
Publication Date: 2013-May-08

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The IP.com Prior Art Database

Abstract

Mud displacement forms an essential part of a successful cementing job. The displacement of mud alone doesn’t ensure good bonding of the cement to the walls of the formation and casing. This is because the mud often leaves behind a mud filter cake on the walls of the formation. This filter cake prevents the cement from bonding to the formation. Traditional industry methods use a specially designed fluid called spacer to ‘erode’ the filter cake. It is imperative thus to know the efficacy of the spacer in removing this cake. The present work proposes a test method that simulates an artificial core, creates filter cake under dynamic shear conditions as well as HPHT conditions, displace/convey spacer into a cell to replace the drilling fluid as in the wellbore using a screw motor at a known shear rate, study the effect of spacer wall shear stress on filter cake at HPHT by monitoring fluid loss and torque on the rotor, displace spacer with cement as in the well bore at predetermined shear and HPHT, allow the cement to set inside the simulated core and then carry out shear bond testing by applying breaking torque using a lab scale electric motor.

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Test Method to Quantify Spacer Efficacy in Cleaning Filter Cake and Study its  Effects on Cement Bond Quality  

Abstract 

Mud displacement forms an essential part of a successful cementing job. The displacement of mud  alone doesn't ensure good bonding of the cement to the walls of the formation and casing. This is  because the mud often leaves behind a mud filter cake on the walls of the formation. This filter cake  prevents the cement from bonding to the formation. Traditional industry methods use a specially  designed fluid called spacer to 'erode' the filter cake. It is imperative thus to know the efficacy of the  spacer in removing this cake.  

The present work proposes a test method that simulates an artificial core, creates filter cake under  dynamic shear conditions as well as HPHT conditions, displace/convey spacer into a cell to replace the  drilling fluid as in the wellbore using a screw motor at a known shear rate, study the effect of spacer wall  shear stress on filter cake at HPHT by monitoring fluid loss and torque on the rotor, displace spacer with  cement as in the well bore at predetermined shear and HPHT, allow the cement to set inside the  simulated core and then carry out shear bond testing by applying breaking torque using a lab scale  electric motor. 

Introduction 

Cementing forms an integral part of well completion and zonal isolation. Of the several factors that  influence a cement job, mud displacement plays a very important role in achieving a good cement bond  to maintain well integrity. During the drilling operation, when drilling mud is circulated, a mud filter cake  often forms on the formation walls. This filter cake while beneficial to the drilling operations, adds  operational difficulties to the process of cementing. Cement traditionally is very selective in the way it  bonds with the casing and formation. Presence of an incompatible mud often leads to a situation where  the mud 'contaminates' the cement. This leads to change in not only the rheological characteristics of  the cement but also the chemical and setting characteristics of the cement. One of the most detrimental  effects of the presence of an incompatible mud cake on the formation/casing wall is that it prevents the  cement from bonding properly with the surface. Poor bonding results in a situation where gas and fluid  from the formation may migrate to different zone leading to failure to maintain zonal isolation by 'fluid  migration'.  


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One of the traditional ways to combat this issue is to remove the mud...