Design of cement pulsation treatment in gas wells - Model and field validation

Document Type

Article

Publication Date

1-1-2005

Abstract

Top cement pulsation (TCP) is an auxiliary cementing technology for enhancing zonal isolation by applying low-frequency hydraulic pressure pulses to the top of the well's annulus immediately after placing cement in the annulus. A properly designed TCP keeps the well overbalanced by delaying the process of cement slurry thickening in the well annulus without pressurizing the well's bottom. As a result, the cement slurry prolongs its liquid state, the thickening time is delayed, and transition time is shortened. The combination of these effects improve cement quality and eliminate gas flow after cementing. Using a hydraulic analogy between low-frequency reciprocation of Bingham fluid and the plug flow, a mathematical model describing the TCP treatment has been developed. The model employs a new formula describing plug flow pressure loss for the pulsed cement slurry. Also, equations have been developed to calculate the compressibility of the well annulus filled with cement and drilling mud. The TCP mathematical model calculates downhole transmission of the top displacement amplitude and pressure attenuation. The model gives the basis for TCP treatment design and efficiency prediction for a given well program and slurry properties. Also presented is an experimental verification of the TCP design model using full-scale pulsation of thixotropic slurry at the LSU well facility. Further verification is given by the field data from TCP treatments of cements in "instrumented" wells equipped with pressure and temperature sensors downhole.

Publication Source (Journal or Book title)

Journal of Canadian Petroleum Technology

First Page

36

Last Page

45

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