Abstract

A survey of cement manufacturers in the Asia Pacific Region revealed that only five companies produce a certified API Class G cement. Because of this, certain countries have been forced to import cement and in many cases ship it great distances. In some situations, API Class G cement can cost three times more than local construction cement. While the authors believe that the API Monogram is an excellent benchmark for oilwell cement, the question is - is it necessary to preclude good local cements from use simply because they are not certified. After all, the key issues for oilwell cement are predictability and performance, not certification.

In the absence of local API Class G cement, the authors propose two ways to use local cement in oilwell applications. First, work with existing construction cement companies to develop cements that consistently meet specifications of the desired API Class and use it in the field. Second, when and where it is applicable, use construction cement for oilwell cementing. The authors are implementing both techniques successfully in parts of South East Asia.

This paper presents historical and technical background as well as laboratory data to support the use of local cements as an alternative to imported API Class G cement. Also, presented are several case studies on the use of local cement in oilwell applications as a means to save drilling costs.

Introduction

Cement forms one of the most important items on an oil rig's material inventory. Its applications in modern oilfield operations include cementing the casing strings in position, thereby providing them with mechanical support and protection, as well as maintaining long-term zonal isolation of the producing formations. Additionally, it is used to isolate or "squeeze-off" water producing zones and to provide "plugs" of high integrity for sidetracking or abandonment.

The first recorded oilfield cementing operation was conducted almost 100 years ago. That first operation took place in 1903 when Frank F. Hill with Union Oil Co. mixed and dumped 50 sacks of cement by bailer to shut off water flow in a California oilwell. After 28 days, the cement was drilled out and the well completed successfully1.

However, it was not until 1910 when A.A. Perkins introduced his 2-plug cementing technique that modern oilwell cementing was born2. Since then, major improvements have been made in both technique and equipment. The introduction of bulk cement in 1940 and the use of special additives to control the slurry properties highlight some of these improvements.

The search for oil has necessitated drilling to progressively greater depths and, consequently, has made the control of slurry properties, particularly thickening time, of paramount importance. The procedures of the 1920's where tons of ice were sometimes added to the mud in an attempt to cool down holes at depths of 6,000 ft were not completely successful, and certainly could not be applied to today's' wells where depths often exceed 20,000 ft.

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