Identifying the constraining factors of PRODUCTION and yield gap is very important. Therefore; this research was performed to identify the PRODUCTION constraining factors of local rice cultivars. All management practices from nursery preparation to harvesting stages for 100 paddy fields of local rice cultivars were recorded through field studies, in Sari, from 2015-2016. In the CPA, the actual and calculated potential yield were 4495 and 5703 kg/ha, respectively and the gap was 1221 kg/ha. The yield gap caused by number of top-dressing variables was 324 kg/ha, equal to 27% of the total yield gap. The yield gap related to previous year of legumes cultivation was 218 kg ha-1, equal to 18% of the total yield variation. Among the 10 variables entered in the CPA model, the effects of top-dress fertilizer application and its application frequency and foliar application were remarkable, which could compensate a significant part of the yield gap (444 kg/ha, 37% of total) in the farmers’ fields by managing these variables. According to boundary line analysis (BLA) finding, actual yield mean on the basis of optimal limit related to 12 variables under study was 5369 kg/ha, with 881 kg/ha yield gap . Mean relative yield and relative yield gap for 12 variables (transplanting date, seedling age, number of seedlings per hill, planting density, nitrogen and phosphorous per hectare, nitrogen before transplanting, harvesting date, lodging problem, pest problem, diseases problem and weeds problem) were 83.64 and 16.35 kg/ha, respectively. Based on the finding, it can be stated that the model precision is appropriate and can be applied for both estimation of the quantity of yield gap and determining the portion of each restricting yield variables.

Mansuri oil field, which is located at the South-West of Iran, has SAND PRODUCTION problem and primary analyses proved the existence of this phenomenon in this field. Generally, there are three methods to evaluate the SAND PRODUCTION state which are empirical, numerical, mathematical, and physical. Considering the numerical capability to analyze complex geometries under high stresses condition, FLAC3D, which is a three-dimensional explicit finite-difference program for engineering mechanics computation, was employed to analyze SAND PRODUCTION in this field. First, the numerical model was calibrated using designed physical model and then, producing intervals and their perforations were modeled by numeric software. Its results showed that not only end-perforation instability is not the sole dominant mechanism in SAND PRODUCTION, but also the effect of adjacent perforations on each other is more important. In this respect, there is an optimum pressure that causes perforations failure and catastrophic SAND PRODUCTION. Mansuri field analyses demonstrated that the downhole pressure at its wells is near predicted optimum pressure and producing intervals are going to catastrophically produce SAND.

Brick is the most widely used construction material. Demolition of buildings and PRODUCTION of construction waste, including clay brick, are dramatically increasing in an alarming rate. The PRODUCTION of traditional bricks such as clay bricks has hazardous impacts on the environment, such as pollution and extensive use of natural resources. This study addressed the application of the geo-polymerization process as an environmental and sustainable method to produce new bricks from clay brick waste and different types of fillers. Accordingly, the powder and grains of clay brick waste, dune SAND, washed SAND, industrial sodium hydroxide, and water glass were utilized to prepare cubic and brick-shaped geopolymer samples with different mix designs and then cured at 70 °C. The samples' compressive strength, water absorption and SEM analysis were examined. According to the results, the highest compressive strength for cubic mortar samples was obtained in the case without filler; for these samples, with mass ratios of water glass to sodium hydroxide solution equal to 1 and 2, compressive strength was 18.45 and 22.15 MPa, respectively. In the brick samples, the highest compressive strength was obtained in the 28-day and 8 M geopolymer samples, which was equal to 25.38 MPa. On the other hand, the geopolymer samples made by SAND filler had higher compressive strength and lower water absorption in comparison to other samples. Therefore, sustainable PRODUCTION of geopolymer bricks from clay brick waste and inexpensive materials as the filler can be a step toward mitigating the environmental impact of construction and demolition waste.

SAND PRODUCTION imposes a considerable cost on the oil industry. In the current study, this phenomenon is studied numerically to better understand the particulate mechanism of SANDing in unconsolidated SANDstones and study the effect of confining stress and pressure drawdown on SAND PRODUCTION. The discrete element method (DEM) is used to simulate the particulate media, and the lattice-Boltzmann method (LBM) is adopted to model the fluid flow through it. The two methods are coupled, and the fluid-solid interaction is modeled using the immersed moving boundary (IMB) method. An in-house computer program is developed based on these methods to simulate the 2D SANDing procedure under radial fluid flow and isotropic stress in the absence of particle cementation. The results show that the number of produced particles and the SANDing rate increase with the increase of confining stress. Also, after the SAND initiation, the SANDing rate in all models decreases due to the formation of SAND arches around the model’s inner cavity. These arches are prone to instability, and new larger arches replace them after their collapse. After examining the effect of fluid pressure difference on SAND PRODUCTION, it is concluded that the pressure difference has little influence on SAND PRODUCTION at relatively low-stress levels. However, at higher stress levels, the pressure difference has a considerable impact on SANDing results as it increases the number of produced particles more than twice with a 50% increase in pressure difference. This study confirms that the 2D coupled DEM-LBM model can properly capture the mechanism of the SAND PRODUCTION phenomenon.

Oil PRODUCTION may be accompanied by SAND PRODUCTION (SP) in the weak SANDstone reservoirs. Fluid flow is an important factor in transporting the separated grains and completing the SP mechanism. In this paper, the effect of fluid parameters, fluid flow, and fluid pressure on the SP is investigated by applying the Discrete Element Method (DEM). Parametric studies show that fluid velocity is reduced by increasing the fluid viscosity, leading to a drop in the SP. In the present study, for an accurate investigation and discovering the effects of viscosity and drag force, the boundary conditions were applied to retain the fluid velocity as a constant amount. The results showed that viscosity is directly related to SP. Moreover, we found that when the fluid velocity is high, there would be the possibility of catastrophic PRODUCTION in the reservoirs with a heavy oil fluid. The rock reservoir around the well will be loosened as soon as SP is initiated. The results also indicate that SP has a direct relation with fluid pressure, fluid velocity, and confining pressure.

SAND PRODUCTION in SANDstone reservoirs is a vital issue in oil and gas fields due to the damage and economic problems it entails. SAND PRODUCTION leads to many problems such as erosion of facility of well and surface equipment, environmental problems, reduction and interruption in PRODUCTION and Sometimes it causes the loss of wells. Therefore, controlling SAND PRODUCTION from wells prone to SAND PRODUCTION is very important. So far, various methods, including mechanical and chemical, have been proposed and performed to control SAND PRODUCTION, which are consolidated in chemical methods by injecting polymer fluids such as resins, etc. to the SAND formation. The main purpose of this study is to provide aqueous-based resin that, in addition to creating compressive strength and slightly reducing permeability, is environmentally friendly and effective in terms of health and safety in comparison with solvent-based resins. By combining different percentages of resin and its suitable hardener with the produced SAND sample, different core samples were made with different percentages. The fabricated cores were tested for permeability and compressive strength. Experiments showed that the fluid used has the ability to chemically consolidate the SAND and the compressive strength and permeability values also change with the amount of resin and hardener composition.