With the continued growth of petroleum demand, the oil and gas companies are searching in new or unexplored areas. The search is getting extreme in terms of depth, temperature and pressure. In deeper wells, high temperature and pressure and post cementing operations put extreme stresses on the cement sheath and affect the integrity of the cement. In such conditions, the design of cement slurry is very critical and it must possess properties which ensure the durability and long term integrity of cement sheath. The purpose of this study is to evaluate the physical properties of Saudi cement class G with silica flour and admixed with different additives such as fluid loss agent, retarder, expanding agent and friction reducing agent under high temperature and pressure conditions. In this paper, we present the results of experimental investigations conducted on class G cement slurry without additives, as a basis, and cement slurry with additives and silica flour. Free water separation, rheological properties, compressive strength, density, scanning electron microscope (SEM), X-Ray diffraction (XRD), porosity and permeability tests were conducted with and without additives at both room and HTHP conditions.

In this paper, refractory bricks were developed by using locally obtainable materials like red clay and glass sand in Bangladesh. The Preliminary investigation was conducted by measuring the compressive strength of bricks produced by adding a range of materials with red clay in different proportions. It was found that the brick containing 30% white Portland cement and 10% glass sand with red clay (60%) demonstrated the highest compressive strength (36.20 mpa). The suitability of refractory bricks was evaluated by examining their physical and thermal properties. The evaluation of these parameters revealed that the properties are suited with refractory requirements such as low water absorption (4.58%), moderate apparent porosity (13.32%), preferable bulk density (2.64 gm/cm 3 ), less linear shrinkage (3.10%), better refractoriness (1408 ºC), thermal conductivity (1.3 W/m.K) and thermal shock resistance (15 cycles). The mineralogical analysis carried out by XRD exhibits the presence of Quartz and Bavenite phase. The performance evaluation shows that this brick is able to fit most of the criteria of refractory brick needed for practical purposes. Since local materials were utilized, the proposed method can be used for the manufacture of low-cost refractory brick in Bangladesh.

Co-gasification of the fossil fuel with the biomass is considered a very promising clean energy opt-in reduce the greenhouse gas emission. The main objective of this research is to develop a simple and reliable model provided as a preliminary tool to evaluate the performance of the co-gasification of sub-bituminous coal with densified biomass (sawdust pellet, SP). The simulation model using Aspen Plus was validated with the experimental data for minimization of the Gibbs free energy model. Three performance parameter; the calorific value of the syngas (CVsyngas), syngas yield (Ysyngas) and gasification efficiency (ŋGE) were studied along with three different control parameter. The increase of the sawdust pellet blending ratio denoted in a decrease of the CVsyngas, Ysyngas and ηGE ranged from 3.00-6.00 MJ/Nm3, 1.20-2.20 Nm3/kg and 25%-37%, respectively. On the contrary, effect of the gasification temperature at the various blending ratio exhibits an increase for all the performance parameters. In addition, ERair resulted in the decline of the CVsyngas from 8.50 to 1.58 MJ/Nm3 and ηGE from 52 to 15% while vice versa for Ysyngas. Furthermore, it is found that the result obtained from the developed model agrees well with the experimental data that have been conducted in replicate.

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