Abstract

One of the major factors affecting the success of a cement job in the oil-well cementing industry is the concentration of the organic additives used. Some of these additives considered to be critical include retarders, dispersants and fluid-loss additives.

UV/VIS spectrophotometric methods were developed to determine seven additives (two retarders, two dispersants and three fluid-loss additives) independently or in combination. Differential Scanning Calorimetry (DSC) and High-Performance Liquid Chromatography (HPLC) were tried with limited success.

Introduction

Cementing is one of several steps needed for preparing an oil well to produce. An oil well is cemented for many reasons, the most important being to

  • support the casing.

  • prevent caving of the hole.

  • protect pipe from corrosion, and

  • isolate zones and thus prevent mixing different

  • types of fluids, e.g., water and oi1.

Many factors go into the design of a cement Job. Some of the factors that determine the design are type of formation, depth of hole, bottom-hole static and circulating temperatures (BHST and BHCT), availability of water (fresh or salt), etc. This wide range of conditions requires the use of additives for modifying the cement to suit the wellrequirements. Generally, cement additives are classified as the following.

  • Accelerators

  • Retarders

  • Fluid-Loss Control Additives

  • Weighting Agents

  • Dispersants

  • Speciality Materials

Those considered very critical and used for our studies were the retarders. fluid-loss control additives and dispersants.

  1. RETARDER A (RET-A) - a very reliable cement retarder used in wells having a BHCT up to 93.3 °C (200 °F).

  2. RETARDER B (RET-B) - a cement retarder chosen mainly for high-temperature applications usually from 93.3 °C (200 °F) to 204.4 °C (400 °F) BHCT.

  3. DISPERSANT A (DISP-A) - aids in inducing turbulent flow for primary cementing operations.

  4. DISPERSANT B (DISP-B) - a turbulent flow inducer designed for application in wells with BHCT of 93.3 °C (200 °F) or higher.

  5. FLUID-LOSS CONTROL AGENT A (FL-A) - for salt cement systems. It is intended for use in cement systems containing 10 %, to 37 % salt by weight of mix water.

  6. FLUID-LOSS CONTROL AGENT B (FL-B) - for cement slurries prepared with fresh water. It is used to control the rate of water loss from cement systems used in both primary and squeeze cementing operations.

  7. FLUID-LOSS CONTROL AGENT C (FL-C) - designed for use with low-density slurries. It can be used with either water or seawater slurries.

The level of concentrations of these organic additives affected the success of a cement job to a great extent. These additives, depending on the requirements, can be added singly or in combinations. Therefore, method(s) for determining these organic additives were needed. This project was undertaken with the intention of developing a method(s)for determining the amounts of the additives in dry cement blends using either (1) sophisticated analytical instruments or (2) simple portable spectrophotometers that could be used in the field.

BACKGROUND

In most oil-field cementing jobs, the combinations of additives (with respect to the ones in question) include the following.

Keywords:
casing and cementing, drilling fluid selection and formulation, technical meeting, polymer, bhct, cement additive, drilling fluid formulation, drilling fluid property, retarder, petroleum society
Subjects:
Drilling Fluids and Materials, Casing and Cementing, Drilling fluid selection and formulation (chemistry, properties), Cement formulation (chemistry, properties)
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1986. Petroleum Society of Canada
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