Bounding Studies of Cementing Compositions to Pipe and Formations

ABSTRACT

Bonding properties of oil-well cementing compositions as related to field applications have been studied to increase understanding of cement behavior in a well. Phases considered were shear-bond strength and properties of hydraulic bonding. Seven cementing compositions were used in this study.

Shear bond is defined as the bond which mechanically support pipe in the hole. The effect of closed-in pressure on shear bond was determine on various pipe sizes. Shear-bond tests were also made on new and used pipe, evaluation was made of the effect of dry and mud-wet pipe surfaces.

Hydraulic bonding of cements is defined as the ability of cement to help prevent fluid communication. These tests were conducted on cement-pipe and cement-formation interfaces. The cement-pipe interface tests were run under the same conditions as those stated for shear-bond tests. The cement-formation interface tests were made on two sizes of cores using sandtone and limestone formations. These tests were run with and without mud cakes, and the effect of dehydrated and non-dehydrated cement slurries was evaluated

INTRODUCTION

Bonding properties of cement are being studied to improve knowledge and determine bonding ability of present-day cements in oil wells. Types of bonds studied were shear and hydraulic as applied to casing and cement in the hole. Primary cementing compositions tested are listed in Table 1.

Shear bond is defined as the bond between pipe and cement that supports the pipe in the hole. These tests covered the effect of closed-in pressure, coated pipe (mill-finished), uncoated pipe (wire-brushed, rusty, and sand-blasted). The effect of dry or wet pipe surface conditions was also investigated with pipe being wet with either water-base or oil-base mud. Samples for shear-bond tests were prepared as shown in Fig 1A, and shear bonding strength reported as pounds per square inch of bonded surface on the inside pipe.

Hydraulic bong is defined as the bond between pipe and cement, or cement and formation, which helps prevent fluid communication. These tests covered pipe walls, both dry and wet with water-base mud , and formations of sandstone and limestone. The hydraulic-bond strength of pipe to cement was determined as show in Fig 1B. The hydraulic bond between cement and formation was determined by using the apparatus show in Fig1C, Fig 2 show how the formation core is mounted on a backing plate and the installed in a test chamber Fig 3 shows the test chambers mounted and connected to an air-pressure manifold for squeezing fluid against the formation. Hydraulic-bonding data are reported as the hydraulic pressure required to cause fluid movement through the cement-pipe or cement-formation interface.

Table 1

Primary Cementing Composition Tested

1. API Class A Cement


2. 50-50 Pozzolan X Cement - 2 Percent Bentonite


3. 50-50 Pozzolan Y Cement - 2 Percent Bentonite


4. API Class A Cement - 12 Bentonite - 0.5 Percent Ligin Retarder


5. API Class A Cement - 1 Percent Low-fluid-loss


6. Latex Cement


7. Resin Cement

Factors Influencing Bonding Properties of Cement to Casing Under Laboratory Test Conditions