Due to the current global oil price, the sand production is considered undesirable product and the control of sand production is considered as one of the main concerns of production engineers. It can damage downhole, subsea equipments and surface production facilities, also increasing the risk of catastrophic failure. As a result of that it costs the producers multiple millions of dollars each year. Therefore, there are many different approaches of sand control designed for different reservoir conditions. Selecting an appropriate technique for preventing formation sand production depends on different reservoir parameters. Therefore, choosing the best sand control method is the result of systematic study. In this paper the sand production factors and their effects are presented where the emphasis is given towards the sand prediction to determine the probability of producing sand from the reservoir, followed by the correct prevention implementation of sand control method. The combination of these two is presented as a smart control framework that can be applied for sand production management.

The Sinian Dengying Formation in the Sichuan basin is an important potential reservoir for oil and gas exploration in the periphery of the Sichuan basin. Its reservoirs were well developed. And many kinds of fillings which lead to the decrease of pores can be seen in reservoir pores and caves. In this paper, the pore fillings of the Dengying Formation reservoir in Sichuan basin are the object of study. The types and characteristics of the fillings are studied in detail by means of rock slices analysis, cathode luminescence, trace elements and inclusion temperature measurement. The study shows that the fillings include dolomite fillings and siliceous quartz fillings and bitumen fillings. Among them, dolomite fillings can be divided into botryoidal dolomite fillings, foliated dolomite fillings, finely-medium crystalline dolomite fillings and coarse crystalline dolomite fillings. 50%-80% of the pores are filled by the dolomite fillings with botryoidal structure, and the pores can be partially full filled; 0%-20% of pores are filled by foliated dolomite fillings; 20-80% of the pores are filled by finely-medium dolomite fillings; 20-80% of the pores are filled by coarse crystalline dolomite fillings. 1%-5% of secondary pores are often filled by siliceous quartzs, and the pores can be partially full filled. Bitumen fillings often occur after the above-mentioned fillings, and the residual pores are often semi-filled by bitumens, which makes the original pores and throat smaller and reduces the effective porosity and permeability of the reservoir. So, it is a destructive diagenesis. The pore fillings make the secondary porosity in the reservoir significantly lower, which is not conducive to the formation and preservation of the Dengying Formation reservoir.

Diagenesis of clastic rock and hydrocarbon generating capacity are closely related with diagenetic stages. Based on diagenetic evolution, reservoir diagenetic stages prediction method is proposed through making a contrastive study of simulation results and test results using core measurement data. The essence of this method is illustrated and its effectiveness is demonstrated using Ed₂ clastic sandstones in the west of Bozhong sag, Bohai Bay Basin, China. Measurement of paleo temperature (T), vitrinite reflectivity (Ro%) and the proportion of smectite in illite/smectite interstratified minerals (I/S-S%) indicate that there are there types of diagenetic stages in the study area, including early diagenetic stage B, middle diagenetic stage A1 and middle diagenetic stage A2. When only considering T index for diagenetic stages prediction, the simulation results are more conservative than measured data with some situations, and the simulation result using Ro% for diagenetic prediction is less than measured data in some wells. When I/S-S% is used, the two situations above both exist. Because depth, temperature, time duration, pressure and some chemical variables can change synchronously or asynchronously, it is difficult to attribute with certainty the parameters that affect the apparent diagenetic stages evolution series. Diagenetic stage variations can be significantly different in different parts of one sedimentary basin. A synthetic indexes method considering T, Ro%, I/S-S% to predict its distribution, and the simulation result has proved that the reliability of the model has greatly improved.

This paper introduces physical models of drill string whirling and torsional vibrations and analyses the physical models in V.I. Gulyayev's three papers on drill string whirling and torsional vibrations: “V.I. Gulyayev, L.V. Shevchuk, Drill string bit whirl simulation with the use of frictional and nonholonomic models, Journal of Vibration and Acoustics 138(1) (2016) 011021”, “V.I. Gulyayev, L.V. Shevchuk, Nonholonomic dynamics of drill string bit whirling in a deep bore-hole, J Multi-body Dynamics 227(3) (2013) 234-244” and “V.I. Gulyayev, SN Hudoliy, O.V. Glushakova, Simulation of torsion relaxation auto-oscillations of drill string bit with viscous and coulombic friction moment models, J Multi-body Dynamics 225 (2011) 139-152”. This work finds that the physical models described in these three papers are clearly incorrect.

The rocks may be classified as Archie rocks or Non-Archie rocks, depending on the link between pore structure and resistivity of the rock. For carbonate rocks, keeping this factor in view, the applicability of Archie's law tends to be unreasonable and employing Archie's equation will ultimately lead to inaccurate estimates of the water saturation. Numerous investigators have reported models that forms a link between laboratory results and field well logs to determine water saturation in intricate pore systems. In case of complex systems, Archie's law fails to correctly define the resistivity-index curves. In addition, it is imperative to carry out investigations at lower saturation values in order to elaborate the non-Archie characteristics. This brings the dual and triple porosity conductivity models into the equation. As these models are essential in defining the considerable changes of the resistivity-index curves, both qualitatively and quantitatively. The linkage between the two models is depicted electrically in series or in parallel. Moreover, it is possible to have a combination of the two configurations. As a result, the experimental results can be modeled accurately using least parameters.

This work presents two models to determine water saturation in carbonate rocks, containing dual and triple porosity systems. This study also investigates the impact of different influential parameters such as saturation exponents, conductivity ratios, and pore volume fraction of each network systems, on the new models. Finally, the effect of each parameter is individually studied and the sensitivity analysis on the RI curves is produced. A new approach to apply these models is also explained which requires the use of NMR log, mercury injection capillary pressure (MICP) measurement, and simple plotting techniques to determine the water saturation. The proposed new models help petrophysicists to estimate water saturation in Non-Archie rocks, containing double and triple porosity network systems.

There have been many attempts to improve the filtration control of water based muds under High Pressure High Temperature (HPHT) condition using a cost effective approach. Nano particles are perhaps the best option considering their successful applications reported in many studies. However, they are often expensive and pose unfavourably changes on the rheology of the muds. In this paper, an attempt was made to show the application of Nano Glass Flakes (NGFs) as a cheap but effective nano particle to control the filtration of water based muds under HPHT conditions. Performing a series of rheology, filtration and conductivity tests on the mud samples with unmodified NGFs revealed that this nano particle increases the mud rheology, yield point and gel strength of the mud with a slight impact on the filtration loss. However, by modifying the surface charges of NGFs with a cationic surfactant, filtration loss was significantly reduced without any severe impacts on the mud rheology. Considering the conductivity of the mud which increases by adding the modified NGF, this nano particle might be a good choice to improve the overall performance of water based muds under HPHT conditions.

The objective of this paper is introducing practical solutions for stabilized pseudo-steady state productivity index and pressure behaviors and flow regimes of multiple vertical wells depleting closed rectangular reservoirs. It introduces full understanding of reservoir performance during transient and pseudo-steady state flow using pressure and pressure derivative patterns and productivity index and productivity index derivative schemes. The practical solutions proposed in this study are relied on a new approach for accurate estimation of starting time of pseudo-steady state flow and stabilized productivity index by applying productivity index derivative that converges mathematically to zero at the beginning of this flow. It is also an attempt for pointing out the optimal reservoir configuration that can give maximum stabilized pseudo-steady state productivity index for different wellbore types and distributions in the drainage area.

Several analytical models are used in this study for describing pressure drop and productivity index behavior of multiple vertical wells considering different reservoir configurations and different wellbore types and locations. These wells were assumed either fully or partially penetrate the formations. These pressure models are justified to generate two pressure derivatives, one represents the derivative of time dependent pressure drop and the second represents the derivative of time-invariant pressure drop. The two derivatives are used for determining the starting time of pseudo-steady state flow and stabilized productivity index when both converge and mathematically become identical. These models are used also to generate several plots for time-invariant or stabilized pseudo-steady state productivity index for different reservoir geometries considering different wellbore conditions. The maximum stabilized productivity index is illustrated in these plots and several analytical models for the expected flow regimes are developed using pressure and pressure derivative behaviors of different reservoirs and wellbore conditions.

The outcomes of this study are summarized in: 1) Developing new analytical solutions for pressure distribution in porous media drained by multiple vertical wells. 2) Developing new practical solution for estimating stabilized pseudo-steady state productivity index. 3) Understanding pressure, pressure derivative, and productivity index behavior of finite acting reservoir depleted by multiple vertical wells during transient and pseudo-steady state production. 4) Investigating the impacts of different reservoir configurations and wellbore sizes and locations as well as partial penetration on stabilized pseudo-steady state productivity index.

The novel points in this study are: 1) The optimum reservoir configuration that gives the maximum stabilized productivity index is the rectangular shape reservoir with reservoir length to width ratio of (2−4). 2) Starting time of pseudo-steady state and stabilized productivity index are impacted by wellbore numbers, sizes, and locations. 3) Starting time of pseudo-steady state flow is not affected by partial penetration ratio, however, stabilized productivity index is affected by this ratio. 4) Five spots pattern gives the maximum productivity index compared with other wellbore distribution patterns. 5) Productivity index of diagonally distributed wellbores is greater than the index of wellbores distributed along reservoir length.

In this study, acid fracturing treatments were simulated for a tight limestone reservoir within a shale formation using FRACPRO software. The purpose was to investigate the optimum acid fracturing design that leads to a higher fracture etched length and width, and higher fracture conductivity. Moreover, the impact of the rock-acid contact time and whether to consider a post-flush or fluids flowback, on the acid fracturing outcomes were also investigated. A simple geological model was constructed which consists of different lithological layers. Different acid fracturing design scenarios were considered starting from a single stage of acid injection to multi-stage treatment. In multi-stage acid treatment, alternate acid-slickwater injection was considered. Plain HCl acids with different concentrations and other acids that are already included in FRACPRO database were used. The results showed that the acid loss during post-flush is among the main problems of the acid fracturing in tight carbonate shale reservoir. For the single stage of acid injection, it is recommended to flow back the acid after well shut-in instead of considering a post-flush stage. The multi-stage alternate acid slickwater injection reduces or even eliminated the acid loss. However, it is recommended to inject a slickwater before well shut-in to reduce the rock-acid contact time, thus reducing the formation damage. The results also showed that the created fracture etched width decreases and the fracture etched length increases as the fracturing stages increase. In this study, because of the low carbonate layer permeability and compressive strength, a two-stage alternate 28% HCl and slickwater injection with a post-flush stage is recommended.

Exact determination of pressure-volume-temperature (PVT) properties of the reservoir oils is necessary for reservoir calculations, reservoir performance prediction, and the design of optimal production conditions. The objective of this study is to develop intelligent and reliable models based on multilayer perceptron (MLP) and radial basis function (RBF) neural networks for estimating the solution gas-oil ratio as a function of bubble point pressure, reservoir temperature, oil gravity (API), and gas specific gravity. These models were developed and tested using a total of 710 experimental data sets representing the samples of crude oil from various geographical locations around the world. Performance of the developed MLP and RBF models were evaluated and investigated against a number of well-known empirical correlations using statistical and graphical error analyses. The results indicated that the proposed models outperform the considered empirical correlations, providing a strong agreement between predicted and experimental values, However, the developed RBF exhibited higher accuracy and efficiency compared to the proposed MLP model.

Cyclic steam stimulation (CSS) is widely used for production from heavy oil reservoirs where oil viscosity is manipulated by heat. Many analytical models have been developed to predict the temperature evolution in the reservoir and estimate the oil recovery. However, they often suffer from a number of assumptions which ultimately reduce their efficiency in providing a realistic prediction. In this study, a numerical solution was proposed for two-dimensional heat conduction in heavy oil reservoirs to obtain the temperature evolution during the soaking period. For a better comparison, an industry widely accepted analytical model, knows as the Boberg and Lantz steam stimulation model, together with its modified version later proposed by Bensten and Donohue were considered to examine temperature changes in a synthetic case study. The results obtained indicated that the analytical solutions overestimate the average temperature of the reservoir by 42% after 300 days of injection while the numerical formulation can provide a close prediction. This numerical approach could be a useful tool to estimate the temperature and oil production from heavy oil reservoirs.

A new model was established based on the flow model of the drilling fluid in one-dimensional radial fracture to research the influencing factors on conversion time between lost circulation and overflow for multi-pressure system in fractured reservoirs. And the equation of the conversion time between lost circulation and overflow is obtained by solving the mathematical model. The model were validated by reproducing the field data from Sichuan oil field and the simulation results of references. The influences of consistency index, liquidity index, dynamic shear force, drilling fluid density, drilling fluid intrusion depth, pressure of lost circulation layer, crack width, decreased height of annular liquid level, pressure of high-pressure layer were analyzed. Results indicate that conversion time between lost circulation and overflow increases with the increasing consistency index, liquidity index, dynamic shear force, drilling fluid density, drilling fluid intrusion depth, pressure of lost circulation layer. Conversion time between lost circulation and overflow decreases with the increasing crack width, decreased height of annular liquid level, pressure of high-pressure layer. The time interval of “Hang's Mudding-off” operating should be appropriately less than the conversion time between lost circulation and overflow. Under the premise of ensuring wellbore safety, appropriately increasing the consistency index, liquidity index and dynamic shear force of the drilling fluid can effectively increase the conversion time between lost circulation and overflow in large fractured stratum.

The study aims to explore the corrosion behaviors of 13Cr steel in the high-temperature steam environment. The corrosion behaviors of 13Cr steel were tested in CO₂ auxiliary steam drive environment simulated with the HTHP autoclave. The corrosion morphology and product composition were explored by SEM, EDS, XRD and XPS. The exploration results showed the corrosion rate of 13Cr steel in the high-temperature steam environment was less than 0.04 mm/a. The corrosion behaviors of 13Cr steel were mainly affected by temperature and chloride ion concentration. Temperature inhibited steam condensation and the compactness of Cr-rich layer. With the increase in temperature, more droplets were adsorbed on the surface of 13Cr steel and the compactness of the Cr-rich layer is worse. Chloride ions affects the activity of Fe atoms in the metal matrix. When chloride concentration increased, Fe²⁺ concentration in the solution and FeCO₃ content in the rich-Cr layer were increased and the rich-Cr layer became looser.