Logistics and Design Considerations For Cementing Large Casing Strings in Extended Deviated Wells: A Case History
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 122405, "Logistics and Design Considerations When Cementing Large Casing Strings in Extended Deviated Wells: A Case History," by Borja Latorre, YPF, and Carlos Borquez, Juan Delgado, and Ariel Lueje, SPE, BJ Services, prepared for the 2009 SPE Latin American and Caribbean Petroleum Engineering Conference, Cartagena, Colombia, 31 May-3 June. The paper has not been peer reviewed.
An extended-reach high-angle exploratory well was drilled, targeting a natural-gas zone under Los Barriales Lake, in Argentina. The well consisted of four cemented sections with 20-, 133/8-, 95/8-, and 7×95/8-in. casings, and a maximum deviation of 81°. The final section was completed open hole. Cementing operations were planned for cementing high-angle (and horizontal) wells drilled with oil-based mud (OBM). A detailed design of cementing operations was needed with flexible slurry design and logistics to allow changes during the operations.

Introduction
The demand for natural gas in the region prompted this expansion of natural-gas reserves. An extended-reach exploratory well was drilled to a target under Barriales Cerros Colorados Lake. This area is in the western part of the Loma de la Lata field, the largest gas reservoir in Argentina. The primary objective was the Sierras Blancas formation. The target area was well defined by a correlation with nearby wells and by reinterpretation of old 2D-seismic data. The seismic surveys were run on land before the area was flooded by this artificial lake. To avoid the use of a barge-type drilling rig, it was decided to drill the well from a site adjacent to the lake.
With regard to cementing design and zonal isolation, the main goals were as follows.Ensure integrity and structural support for installation of the wellhead and blowout preventers (BOPs).Provide integrity at the casing shoe to enable drilling operations of the next well section.Provide long-term isolation to ensure an adequate hydraulic seal and prevent future annulus pressure, unwanted fluids invasion, and casing corrosion.Isolate all hydrocarbon-bearing formations and potential leak zones.Avoid annulus-gas migration through the cement matrix.

20-in. Surface Casing
The first section was drilled vertically with a 26-in. bit to 510 m, the top of the Rayoso formation, with a 9-lbm/gal water-based drilling fluid. To determine the real volume of the well, a caliper was run, which also allowed better casing centralization and control of the possible cement excess.

Cementing Design.
The annulus-cleanup design included a crosslinked gelled weighted spacer to remove the filter cake and minimize the cement slurry channeling in the mud. A gel breaker was added to facilitate final disposal of the spacer.
A chemical preflush with nonionic surfactants was designed to achieve maximum mud removal and sufficient contact time; at least 10 minutes of wetting the pipe and formation was required to achieve a high-quality cement bond.