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).
A number of Malaysian mature oil fields have been and are still under investigation for Enhanced oil Recovery (EOR). This includes Water Alternating Gas (WAG), chemical flooding and Foam assisted WAG. This field is one of the most fields under extensive EOR studies for WAG & FAWAG. Despite the promising recovery factor from EOR application there are always the side effects that accompany these processes which are formation damage and injectivity issues. A lot experiments studies shown, when a large number of pore volumes of polymer is injected with medium permeability beyond a critical shear rate, a plugging tendency is observed. This plugging is attributed to a damage mechanism called "bridging adsorption" in which stretched polymer macromolecules form numerous bridges across pore throats. At the same time, causes fine migration issue. In this study, the effects of fines migration, clay swelling and injectivity were investigated in separate core floods studies (one test for fines migration, one test for clays swelling and three for chemical injectivity). For the fines migration study, the core flood test to investigate the critical flow rate of the seawater injection shows fines migration problem as observed from sea water injection of intermediate critical flow rate for fines migration in the core. For clays swelling the permeability reduction test and pH measurement with decreasing salinity indicates a critical salinity much less than the sea water salinity and sea water is the proposed medium for the EOR chemical in this field. Moreover, SEM investigation analysis result shows that most of the damage is due to fine migration caused by the velocity flow rate of the injection sea water. For injectivity study, core flood tests were conducted with injecting surfactant polymer (SP) solution and with surfactant and polymer individually. The results show that while minimum damage of less than 30% is typically expected in this type of test with permeability resistance factor of less than 3, what was actually obtained in this test is about 95% damage and permeability resistance factor (PRF) is 23 compared to KPI of 3. The results also indicate that incompatibility between the surfactant and polymer could be one of the reasons for permeability decline. This is because while injecting the chemicals separately no serious injectivity issue is observed. Introduction EOR studies prior to field application have recently enjoyed global attention due to several reasons including declining oil production below par primary and secondary recovery, high crude oil price and increasing energy demand which is growing at approximately 1.5% per year (Du, K., et al, 2011). Laboratory testing in support of field application is critical to minimize field application failures. This paper addresses possible risk of formation damage due to fine migration, clay swelling and polymer absorption during Foam Assisted Water Alternating Gas (FAWAG) process proposed for the field. The offshore field is located 170 km away from West- Malaysia land. Currently this field is being considered for enhanced WAG process called Foam assisted Water Alternating Gas (FAWAG). In this process it is proposed to alternate polymer surfactant with gas instead of water. Surfactant is proposed to precede the gas injection, which will generate foam in-situ. Foam so generated along with the polymer is expected to improve the displacement efficiency by virtue of better mobility control, once implemented, This field will be the first such application in Malaysia.
Among the different Enhanced Oil Recovery methods being implemented in the matured fields of Malaysia,Immiscible Water Alternating Gas (iWAG) appears to be the most viable option. However, reduction in well injectivity and productivity would be very harmful to this process and render it ineffective. Therefore, extensive laboratory testing, interpretation and integration have been performed to reach the conclusions and recommendations presented in this paper.The target reservoirs in the Bokor are made up of unconsolidated and very heterogeneous rock with high permeability streaks. The mineralogy of the target reservoirs shows over 10% of clay, with abundance of kaolinites and illites which tend to cause fines migration and mixed layer illites/smectite which can swell. Therefore special handling of core samples is necessary for the laboratory testing; this includes flow through cleaning and critical point drying. The aim of the study is to establish the potential mechanisms of formation damage during the iWAG progress and determine preventive, mitigative measures and provide guidelines for treatment if damage occurs. The main focus is on formation damage by fines migration, dirty injection fluids (Mechanically induced damage)and clay swelling and de-flocculation (Chemical induced damage -fluid rock interaction) effect to Bokor field. The laboratory tests performed includes capillary suction time, filtration level test, critical velocity and fines stabilizer test, constant rate injectivity test and formation damage by iWAG injection test.Key areas of interesting findings include (1) Potential formation damage mechanism during the iWAG process (2) Strategies to prevent damage and improved injectivity, (3) Recommended treatment frequency based on injection half-life established in this study and (4) Field monitoring strategies.
This review focuses on the potential of microalgae biomass in producing biopolymer materials. Microalgae have gained attention as a sustainable and renewable source of energy and other useful products such as biofuels, pharmaceuticals, and cosmetics. One promising application of microalgae is as a source of biopolymers, which can be used as a sustainable alternative to traditional petroleum-based plastics. The review is conducted through a comprehensive search of electronic databases, screening of relevant articles, and synthesis of information obtained from the selected studies. The review also critically evaluates the strengths and limitations of the existing research on the potential of microalgae biomass in producing biopolymer materials. The outcomes in this review highlights key findings related to the potential applications of microalgae biomass in producing biopolymers and identifies areas for future research. The conclusions and recommendations of this review are important for guiding the development of sustainable and environmentally friendly biopolymer materials.
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