Using Lightweight or Low Viscosity Preflushes for Primary Cementing of Surface Casing

2018 ◽  
Author(s):  
Amir Maleki ◽  
Ian Frigaard
Keyword(s):  
Contact Time ◽  
Drilling Fluid ◽  
Two Dimensional ◽  
Drilling Mud ◽  
Dimensional Model ◽  
Chemical Cleaning ◽  
Low Viscosity ◽  
North Eastern ◽  
Primary Cementing ◽  
Intermediate Density

Preflushes are often used as part of the sequence of fluids pumped in primary cementing. Usually two functions are served by preflushes: I) to wash the drilling fluid ahead, by a combination of turbulence and chemical reaction; II) to provide a chemically compatible spacer between the lead slurry and the drilling mud. In some cases a wash precedes a spacer, but often only a single preflush is used. We consider well parameters typical of surface casing cementing in North Eastern British Columbia. Using a two-dimensional model of annular displacement flows, we show that the wash concept is flawed. In particular, in a sequence of simulations varying from intermediate density to low density we show that the wash progressively advances ahead of the lead slurry, channeling rapidly up the wide side of the annulus. Even when fully turbulent, it is ineffective at displacing mud from around the annulus, invalidating the motivation of chemical cleaning through contact time. Furthermore, the advance along the wide side of the annulus drains the volume of fluid separating the cement from drilling mud. Thus, the idea that the wash provides a barrier between slurry and and mud is invalid.

Experimental Study of the Impact of Drilling Fluid Contamination on the Integrity of Cement-Formation Interface

2012 ◽  
Author(s):  
Nnamdi Agbasimalo ◽  
Mileva Radonjic
Keyword(s):  
Drilling Fluid ◽  
Drilling Mud ◽  
Overburden Pressure ◽  
Interface Zone ◽  
Fluid Displacement ◽  
Before And After ◽  
Zonal Isolation ◽  
Primary Cementing ◽  
Flow Through ◽  
The Impact

Primary cementing is performed during drilling and completion of wells mainly to provide zonal isolation. Ideally, 100% drilling fluid displacement should be achieved during cementing. This is difficult to achieve and some mud is left on the wellbore walls. This study investigates the effect of the undisplaced mud on the integrity of the cement-formation interface. Flow-through experiments were conducted at 14.48 MPa (2100 psi) overburden pressure and temperature of 22° C (72° F) with cement-sandstone composite cores and brine at a flow rate of 1 ml/min. The cement-sandstone composite cores had 0% and 10% drilling mud contamination respectively. Variations in the permeability of the composite cores were recorded throughout the flow-through experiments by measuring the pressure drop across the composite cores. The composite cores were characterized before and after the flow-through experiments to delineate the alterations in the composite cores due to the flow-through experiments. Higher pH values were observed in the effluent brine from the 10% mud contaminated core than the 0% mud contaminated core due to increased dissolution of cement. Microtomography revealed higher porosity at the interface zone of the 10% mud contaminated core. These show that mud contamination has a deleterious effect on the cement-sandstone interface and may create pathways for inter-zonal communication.

Commitment to pro- versus counter-attitudinal behavior and the dynamics of social representations

2002 ◽  
Vol 61 (1) ◽  
pp. 34-44 ◽  
Author(s):  
Eric Tafani ◽  
Lionel Souchet
Keyword(s):  
Higher Education ◽  
Social Representations ◽  
Cognitive Restructuring ◽  
Social Representation ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Social Actions ◽  
The Social ◽  
Two Dimensional Model ◽  
Students Attitudes

This research uses the counter-attitudinal essay paradigm ( Janis & King, 1954 ) to test the effects of social actions on social representations. Thus, students wrote either a pro- or a counter-attitudinal essay on Higher Education. Three forms of counter-attitudinal essays were manipulated countering respectively a) students’ attitudes towards higher education; b) peripheral beliefs or c) central beliefs associated with this representation object. After writing the essay, students expressed their attitudes towards higher education and evaluated different beliefs associated with it. The structural status of these beliefs was also assessed by a “calling into question” test ( Flament, 1994a ). Results show that behavior challenging either an attitude or peripheral beliefs induces a rationalization process, giving rise to minor modifications of the representational field. These modifications are only on the social evaluative dimension of the social representation. On the other hand, when the behavior challenges central beliefs, the same rationalization process induces a cognitive restructuring of the representational field, i.e., a structural change in the representation. These results and their implications for the experimental study of representational dynamics are discussed with regard to the two-dimensional model of social representations ( Moliner, 1994 ) and rationalization theory ( Beauvois & Joule, 1996 ).

Pulse Antennas: Accurate Solution of Two-Dimensional Model Problems for Structures with Gratings as Dispersive Elements

2001 ◽  
Vol 55 (8) ◽  
pp. 14
Author(s):  
A. I. Vyazmitinova ◽  
V. L. Pazynin ◽  
Andrei Olegovich Perov ◽  
Yurii Konstantinovich Sirenko ◽  
H. Akdogan ◽  
...  
Keyword(s):  
Accurate Solution ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Dimensional Model
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