The Utilization of Malaysian Local Bentonite as an Extender and Free Water Controller in Oil-Well Cement Technology

Abstract

This paper presents the results of experimental studies for Malaysian bentonite from Sabah (Lahad Datu and Tawau areas) application in oil- well cementing as compared to world wide commercially used Wyoming bentonite of USA. Samples were dried, grounded and sieved into particle size of 75(m. The experiments include XRD & XRF techniques to determine the chemical compositions and mineralogical contents of bentonite. Methylene blue tests were carried out to estimate the value of cation exchange capacity (CEC) in order to determine the approximate montmorillonite content. In the cement performance tests, class-G cement slurry mixed with bentonite in the range of 2%- 16% BWOC. The cement slurries were tested in accordance of API Specification 10. Dry and wet treatment processes were also conducted for the Malaysian bentonite to upgrade its performance. From laboratory investigations, it showed that Malaysian bentonite has less content of montmorillonite mineral and more impurity materials such as quartz, kaolinite, illite, muscovite and hematite, while Wyoming bentonite considered as high- quality bentonite. Malaysian bentonite has low values of CEC which had been improved after treatment processes. Malaysian bentonite has low degree of swelling. The free water of the cement slurry increased with the increase of bentonite concentrations as compared to Wyoming bentonite. On the other hand, after treatment processes, the free water decreases in the cement slurry with bentonite concentrations increased. The Lahad Datu's bentonite had lowered slurry density after the treatments than the Tawau's bentonite. Introduction Cement extender reduces slurry density and lower hydrostatic pressure during cementing operations, which in turn will help prevent the breakdown of weak formations and loss of circulation. It also reduces the amount of cement needed for the cementing operation. Since it is less expensive than cement, it brings considerable savings. Three types of extender are normally used: water extender, low-density aggregate, and gas. Water is the commonest and cheaper extender for cement slurries. The more water that can be added to the slurry, the greater its volume or yield and, of course, the lower the slurry's density. Water extender allows the addition of water to the slurry while ensuring that solid remains in suspension, extenders such as clay and various water viscosifying agents allow the addition of excess water to achieve slurry extension. Such extenders maintain a homogeneous slurry, and prevent the development of excessive water. Low-density aggregate is material that has density less than Portland cement. Therefore, the density of the cement slurry is reduced when significant quantities of such extenders are present (Nelson, 1990). It can be obtained from volcanic ash, diatomaceous earth and fly ash. Gases such as nitrogen or air are used to prepare for lower density cement slurry without additional water. However, the disadvantage of extender is decreasing in the final compressive strength and the permeability of the set cement is increased. Extenders such as bentonite, foamed cement and microspheres decrease the cement slurry density and final compressive strength at 100oF after a 24-curing-hour period. Although clay is one of the commonest minerals, it is not easy to define precisely. It can be said to be material of colloidal or near colloidal particle-size, made chiefly of hydrous aluminium silicates. The most frequently used clay-base extender is bentonite, a naturally occurring clay consisting largely of the mineral montmorillonite. This mineral has an expanding lattice i.e., water molecules can be incorporated in and around its structure. The extending properties of bentonite are greatly enhanced by mixing with the water and allowing it to hydrate completely prior to mixing with the cement (Dowell Schlumberger, 1989).

Field Test for Real Time Monitoring of Piezoresistive Smart Cement to Verify the Cementing Operations

“…(8) and also the stress in the cement sheath using Eqn. The two-probe method was effective in measuring the bulk resistance of the drilling fluid, and smart cement slurries.…”

“…(8) and also the stress in the cement sheath using Eqn. Hence, it is possible to predict the pressure in the casing using Eqn.…”

Aplikasi Bentonite Lokal Terhadap Nilai Compressive dan Shear Bond Strength Suspensi Semen Sumur Minyak

“…Sebagai parameter pembanding ini, suspensi semen ini akan diuji untuk mendapatkan nilai Compressive strength(CS) dan Shear Bond Strength, yang merepresentasikan kemampuan suspensi semen gaya ekternal dan daya ikat supsensi semen terhadap casing dan formasi [4]. Penggunaan bentonite lokal ini terbukti efektif dalam menurunkan densitas suspense semen [5]. Melalui penelitian ini, pengembangan material lokal sebagai aditif pengganti dapat meningkatkan daya saing produk lokal di dunia industri minyak.…”

The Effects of Temperature Variation on the Performance of Oil Well Cement Slurry Formulated With Rice Husk Ash and Eggshell Powder Ad-Mixtures Extender

“…In reducing slurry density, the ultimate compressive strength is reduced the thickening time is increased [28]. For example extenders such as bentonite, foamed cement and microspheres decrease the cement slurry density and final compressive strength at 100°F (38°C) after a 24-hour curing period [27]. Behavior of extenders was confirmed by an experiment conducted by [32] on the relationship between thickening time and extender.…”

“…The reaction of these additives with the cement and the interaction between Many formations will not support long cement columns of high density slurries, these slurries weights need to be reduced to protect formations that have low fracture gradient or for economics purposes. To reduce the weight of cement slurries, extenders are used [27]. Extenders are also known as water adsorbing or lightweight inert materials [29].…”