Hassi Messaoud Research Articles

Fuzzy multi-criteria approach for criticality assessment and optimization of decision making

Failure mode, effects, and criticality analysis (FMECA) is a proactive quality tool that allows the identification and prevention of the potential failure modes of a process or product. In a conventional FMECA, for each failure mode, three risk parameters, namely frequency, non-detection, and severity are evaluated and a risk priority number (RPN) is calculated by multiplying these parameters to assess one signal criticality. However, in many cases, it suffers from some shortcomings regarding the decision-making and the situation where the information provided is ambiguous or uncertain. This paper describes a new fuzzy multi-criticality approach for improving the use of FMECA by treating FMECA as a fuzzy multi-criteria optimization model. The new approach bases on replacing the calculation of a single criticality with a fuzzy inference system for improving the criticality evaluations which offers five partial criticalities that efficiently and separately calculate the impact of a failure on the environment, personnel, production, equipment, and management. In addition, an analytical hierarchy method (AHP) is used to calculate the priorities weights for each partial criticality and construct a criticality matrix in order to improve the relevance of decision-making. Furthermore, a real case of LPG storage system for ZCINA Hassi Messaoud in Algeria is provided to illustrate the practical implementation of the suggested approach and extremely shows the pertinence of the suggested fuzzy model as decision-making tools in preventing industrial risks with providing encouraging results regarding the criticality estimation and improve decision-making by prioritizing “preventive –corrective actions” and determine the efficient action for each partial criticality to control the risk effectively.

Toward Separation and Characterization of Asphaltene Acid and Base Fractions

Chemical inhibition of asphaltene deposition is considered a cost-effective way to prevent the harsh consequences of asphaltene instability in the produced crude. Thus, a careful screening of asphaltene inhibitors is crucial for an efficient prevention. However, the characteristics of asphaltenes such as their acid–base properties will influence the selection of an asphaltene inhibitor and the inhibition mechanism. Therefore, improved knowledge on asphaltene acidic and basic fractions is important. In this work, the separation of asphaltenes into acid, base, neutral, and amphoteric fractions was performed. Among the existing techniques to fractionate asphaltenes, the method of Ramljack was adopted and applied on a light oil extracted asphaltene. However, this oil was sampled from one of the wells in the Hassi Messaoud field in Algeria that experienced a recurring deposition of asphaltenes. The results of asphaltene fractionation reveal that the half composition of this heavy part of crude oil is active functions gathered acid and base components. However, the main contribution is reported to the neutral fraction. The characterization results of infrared and elementary analyses show that both active fractions are aromatic and polar. Moreover, the acid fraction contains in its structure carboxylic acids, phenols, sulfoxide groups, and aliphatic chains, while the structure of the base fraction contains amines, sulfoxide groups, and aliphatic chains.

High-frequency monitoring of anomalous methane point sources with multispectral Sentinel-2 satellite observations

Abstract. We demonstrate the capability of the Sentinel-2 MultiSpectral Instrument (MSI) to detect and quantify anomalously large methane point sources with fine pixel resolution (20 m) and rapid revisit rates (2–5 d). We present three methane column retrieval methods that use shortwave infrared (SWIR) measurements from MSI spectral bands 11 (∼ 1560–1660 nm) and 12 (∼ 2090–2290 nm) to detect atmospheric methane plumes. The most successful is the multi-band–multi-pass (MBMP) method, which uses a combination of the two bands and a non-plume reference observation to retrieve methane columns. The MBMP method can quantify point sources down to about 3 t h−1 with a precision of ∼ 30 %–90 % (1σ) over favorable (quasi-homogeneous) surfaces. We applied our methods to perform high-frequency monitoring of strong methane point source plumes from a well-pad device in the Hassi Messaoud oil field of Algeria (October 2019 to August 2020, observed every 2.5 d) and from a compressor station in the Korpezhe oil and gas field of Turkmenistan (August 2015 to November 2020, observed every 5 d). The Algerian source was detected in 93 % of cloud-free scenes, with source rates ranging from 2.6 to 51.9 t h−1 (averaging 9.3 t h−1) until it was shut down by a flare lit in August 2020. The Turkmen source was detected in 40 % of cloud-free scenes, with variable intermittency and a 9-month shutdown period in March–December 2019 before it resumed; source rates ranged from 3.5 to 92.9 t h−1 (averaging 20.5 t h−1). Our source-rate retrievals for the Korpezhe point source are in close agreement with GHGSat-D satellite observations for February 2018 to January 2019, but provide much higher observation density. Our methods can be readily applied to other satellite instruments with coarse SWIR spectral bands, such as Landsat-7 and Landsat-8. High-frequency satellite-based detection of anomalous methane point sources as demonstrated here could enable prompt corrective action to help reduce global methane emissions.

Modeling In-situ tectonic stress state and maximum horizontal stress azimuth in the Central Algerian Sahara – A geomechanical study from El Agreb, El Gassi and Hassi Messaoud fields

Central Algerian Sahara hosts many prolific hydrocarbon accumulations in the Paleozoic successions. In this work a contemporary stress field of the Saharan platform has been evaluated using the dataset from recently drilled wells in El Agreb, El Gassi and Hassi Messaoud fields. A pore fluid pressure gradient of 0.56 PSI/feet is interpreted from the in-situ measurements in the Paleozoic reservoir units. Vertical stress (Sv) modeled from the bulk-density data indicates an average of 1.02 PSI/feet gradient. Rock elastic property-based approach is employed to model the magnitudes of minimum (Shmin) and maximum horizontal stress (SHmax) components, which were calibrated with leak off test/minifrac and breakout widths, respectively. Paleozoic stress profiles reveal Shmin/Sv range of 0.74–0.84, while SHmax/Sv varies between 1.1 and 1.33. Subsurface stress distribution indicates that the present-day stress field in the Saharan platform is principally strike-slip faulting (SHmax > Sv > Shmin). A cumulative 1490 m of B-D quality wellbore breakouts, inferred from the acoustic image logs, suggest a NW-SE/WNW-ESE SHmax orientation, which is parallel to the absolute African plate motion and Africa-Eurasia plate convergence direction, implying ridge push force to be the dominant contributor to the tectonic stress field. Mean SHmax orientation shows slightly anticlockwise rotation (126°N to 144°N) from south (El Agreb) to north (Hassi Messaoud field). Inferences are discussed regarding the fault slip potential and hydrocarbon reservoir development.

Fluoride-bearing groundwater in the complex terminal aquifer (a case study in Hassi Messaoud area, southern Algeria): hydrochemical characterization and spatial distribution assessed by indicator kriging

According to the World Health Organisation (WHO), the human consumption of water containing a high concentration of fluoride (> 1.5 mg/l) can increase significantly many health problems such as dental and skeletal fluorosis. This study investigates fluoride abundance, origin, and its spatial distribution in groundwater from Complex Terminal (CT) aquifer in Hassi Messaoud area (Southern Algeria) where the CT water constitutes the main source of drinking water with a high daily intake. Available water wells were sampled and analysed on their major physico-chemical parameters including fluoride content. Hydrochemical characterization was constrained using the Durov diagram together with a PCA statistical treatment. The saturation indices were computed and used to track fluoride origin. The spatial distribution of fluoride in the studied aquifer was mapped by indicator kriging (IK). The results show that fluoride content ranges from 1.6 to 2.9 mg/l (average = 2.1 ± 0.4 mg/l) exceeding WHO drinking water standards. The Durov diagram, PCA and SI indicate that water acquires mineralization principally by leaching of evaporite minerals. Furthermore, SI evidences that fluoride concentration in water increases with CaCO3 precipitation leading to CaF2 dissolution. IK spatial distribution allows estimating the probability of not exceeding (2.1 mg/l) critical threshold. The cross-validation displays good performance of IK estimation (mean error = 0.05; mean standard error = 0.09). The obtained map shows a low to moderate probability of not exceeding the selected threshold in the whole aquifer. Therefore, the use of CT water for human consumption poses a risk to public health. These results can be used in water management framework and for selecting an ideal position to drill new boreholes for drinking water.

Intermittent Gas Lift Used in Hydrate Mitigation and Flare Reduction in Algeria

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 191542, “Hydrate Mitigation and Flare Reduction Using Intermittent Gas Lift in Hassi Messaoud, Algeria,” by Ala Eddine Aoun, SPE, Faouzi Maougal, and Lahcene Kabour, Sonatrach, and Tony Liao, SPE, Brahim AbdallahElhadj, and Sabrina Behaz, Halliburton, prepared for the 2018 SPE Annual Technical Conference and Exhibition, Dallas, 24–26 September. The paper has not been peer reviewed. Hassi Messaoud is a mature oil field with more than 1,100 production wells. Approximately half of the wells are natural flow and the other half use continuous gas lift (CGL) with concentric (CCE) strings. To reduce the usage of the high volume of lift gas, intermittent gas lift (IGL) was selected in a pilot project to evaluate its applicability in the field for wells characterized by high gas/oil ratio (GOR) and without continuous concurrent water injection (with lift gas) to dissolve salt•deposited•downhole. Production Overview Field production began in 1957. During the first 20 years, all production wells were naturally flowing; in 1980, gas lift was introduced into the field development and has remained the only artificial-lift method. Electrical submersible pumping systems have been introduced into the field recently. Of the production wells, 795 are flowing while 376 are shut in for a variety of reasons. Among the flowing production wells, 409 are naturally flowing and 386 are artificial-lift wells. Production fluids are processed by 25 separator stations throughout the field. Gas usually is compressed first at the satellite level; then, at the central processing facilities, the gas is further compressed to the pressure required for injection into the reservoir. Water is treated by the addition of surfactants. The treated water is pumped into the water-injection network to be used in both reservoir-pressure maintenance and salt wash in wells. In the field’s first years, the oil-production rate increased quickly as the number of wells grew. Since 2007, oil production has declined quickly in naturally flowing wells. The steady increase in oil production from gas-lift wells offset the fast production decline in the full field. However, the oil production from gas-lift wells has leveled off during the past 2 years, while the production from naturally flowing wells recovered slightly. The gas lift wells contribute approximately 40% of the field production. Combined Gas Network for•Reservoir Gas Injection and Gas Lift A specific challenge of the Hassi Messaoud field operation is the highly complex gas network, in which the gas-lift network is attached to the gas- injection network for reservoir-pressure maintenance. The gas lift was grown organically out of the reservoir gas-injection network. Initially, when only a small number of wells needed gas lift, this approach might have been cost- effective, but the increasing number of gas-lift wells meant that different methods had to be•considered.

Study the formation of the deposit resulting from the sulfate-reducing bacteria on the steel surface of oil pipe N80

This article examines the components of formed deposits on the surface of the petroleum pipes by Sulfate-Reducing Bacteria in the region of Hassi Messaoud (south of Algeria). These bacteria were found in the wells of water and oil. However, we find the problem of bacterial corrosion in the circuits of production and injection when petroleum is extracted. This bacterial corrosion occurs when petroleum which contains water touched the pipes for well long enough to be able to start corrosion. This problem results to the formation of deposits on the inner surface of pipes which lead to the risk of clogging. In this work, we study the deposit resulting from bacterial corrosion on the surface of N80 steel samples and we have identified the most important components of the deposits resulting from the phenomenon of bacterial corrosion

Influence of the Clay Content and Type of Algerian Sandstone Rock Samples on Water–Oil Relative Permeabilities

The objective of this work is to study the effect of certain factors on oil–water relative permeability curves following a considerable drop in the production of certain oil wells at the Hassi Messaoud field in southern Algeria. In the present study, oil–water relative permeability experiments and irreducible water (Swᵢ) and residual oil (Sₒᵣ) saturations have been investigated. The effect of the clay particle content in the samples (such as illite and kaolinite) on oil recovery is investigated. Indeed, other factors, such as injected pressure, wettability alteration, and petrophysical properties, of the reservoir rock interact with each other and, particularly, in the presence of injected Albian water. Results of the waterflooding experiments show that oil recovery (IOP) increases with increasing clay content, namely, kaolinite and illite type; this IOP is clearly higher for plugs containing more kaolinite than illite. The tested samples have water-wetting behavior, showing a decrease in Sₒᵣ and an increase in Swᵢ, and are characterized by a strong presence of clays, 70% kaolinite and 30% illite, with a breakthrough from about 40 to 50%.

Depth effect on sandstone strength properties

Abstract The present article focuses on the study of different physical-mechanical parameters; it presents the results of a preliminary investigation aimed at experimental characterization. To simulate the mechanical behavior of the rock, a reference material needs to be chosen. The reference material selected is Sandstone, which is commonly used in this field of study. The behavior of sandstone from the region of Hassi Messaoud, which is well known for its petroleum operations, deals mainly with different mechanical sandstone properties and their varying strengths. The relationships between different depths and both of the mechanical sandstone properties were evaluated. As a result, useful relationships were found for different depths and the following properties: uniaxial compressive and triaxial test, Young's modulus and Poisson ratio.

A Preliminary study of relationships between thermal conductivity and petrophysical parameters in Hamra Quartzites reservoir, Hassi Messaoud field (Algeria)

In geothermic studies, the thermal conductivity (TC) is an essential parameter needed to calculate heat flow in rocks. It is obtained generally with high accuracy from laboratory measurements. The methodology proposed in this paper is to estimate the TC, which depends on many parameters; such as mineralogy, porosity, shape of voids and nature of contact between grains, based on linear and nonlinear relationships. In order to predict the thermal conductivity from other petrophysical parameters in the Hamra Quartzites reservoir, we have measured porosity, density and permeability, for dry samples taken from core wells. The correlation coefficients (R) were calculated between thermal conductivity and other petrophysical parameters for all samples. The results show that, the correlation coefficient is moderate between TC and the porosity, weak between TC, density and permeability. To improve these correlations, samples were classified into cemented and uncemented sets. A minor improvement on the correlation coefficients is noted between TC, density and porosity in uncemented samples, with values equal 0.51 and 0.73, respectively. The application of Radial Basis Function (RBF) neural networks, using density, porosity and permeability as inputs and thermal conductivity as output, permit us to predict the thermal conductivity with high precision. The correlation coefficient between TC estimated by the RBF neural network is the same as that measured in laboratory equaling 0.983.

Potassium-argon timing of episodic mica and illite crystallization in highly indurated Hassi Messaoud (Algeria) hydrocarbon-bearing sandstones

Nanometer to micrometer mica and illite separates of indurated Cambrian and Ordovician oil-bearing sandstones from the Hassi Messaoud field (Algeria) were extracted, x-rayed, observed by scanning and transmission electron microscopy, and K-Ar dated. Electron microscope observations revealed typical euhedral shapes for the mica to illite particles of most size fractions; almost no odd-shaped detrital crystals were detected. The combined results document several generations of mineralogical and morphological identical mica to illite crystals that could not be differentiated by the traditional identification methods. Illite and mica genesis was multiphased with crystallization episodes at 340 ± 10 (ca. Middle Mississippian), 280 ± 10 Ma (ca. early Permian), and 170 ± 10 Ma (ca. Middle Jurassic). Younger than the stratigraphic age of the host rocks, which is incompatible with a detrital origin, the two older mica ages confirm that the hydrocarbon generation and emplacement had to start after the Variscan tectonothermal event and before exhumation of the meta-sediments. The younger K-Ar ages at 135 to 110 Ma (ca. Early Cretaceous) relate to further crystallization episodes, whereas those at circa 295, 265, and 210 Ma probably correspond to variable mixtures of the older and younger mica to illite end-members. Three average K-Ar values are statistically significant: the oldest at 340 ± 10 Ma corresponds to the start of the Variscan tectonic activity, and the intermediate at 280 ± 10 Ma sets its end, both episodes probably modifying the reservoir capacities of the potential hydrocarbon host rocks. The ages at 170 ± 10 Ma identify a further diagenetic activity characterized by illitization of dickite-type precursors in local reservoirs. These younger ages could correspond to the hydrocarbon charge into reservoirs, which stopped diagenetic illitization at a present-day depth of approximately 4000 m (∼13,000 ft).

Experimental investigations of SDS adsorption on the Algerian rock reservoir: chemical enhanced oil recovery case

The adsorption of surfactant on reservoir rocks or sands is one of the main factors that can significantly reduce the effectiveness of surfactant flooding for light oil recovery. The present work consists of study of the interaction between the surfactant sodium dodecyl sulfate (SDS) and the characteristics of Hassi Messaoud rock established using scanning electron microscopy, Fourier transform infrared analysis, Brunauer–Emmett–Teller surface area analysis and optical microscopy. Parametric study of the adsorption tests was carried out at a temperature between 25 and 80 °C. The conductivity method was used to measure the critical micellar concentration of the SDS surfactant in aqueous solutions. The adsorption data were adjusted using five isotherms and two kinetics of the anionic surfactant. The equilibrium conditions for crushed rock samples were obtained after 11 h of adsorption. According to the experimental results, the equilibrium data were well fitted by the Langmuir isotherm for sandstone sample at all temperatures. The pseudo-second-order model best describes the kinetics of the adsorption process. Furthermore, the adsorption process is exothermic. Several statistical error analyses were applied to evaluate the performance and accuracy of the proposed experiment. A systematic investigation is very useful for selecting an appropriate surfactant for enhanced oil recovery application and reservoir stimulation in the petroleum industry.

Inhibition of asphaltene flocculation in light crude oil: effect of pressure, temperature and inhibitor concentration

In this study, a light crude oil sample was taken from Hassi Messaoud field to characterize its physicochemical properties. The asphaltene flocculation onset was determined in the dead oil by Flocculation Titrimeter equipment. The petroleum resins have been extracted from the same crude oil and tested as an inhibitor of asphaltene flocculation then their efficiency has been studied at different conditions of pressure and temperature. The results point out that the extracted resins may have two different effects on the onset point depending upon the operator conditions and the concentration of the added resins to crude oil.

A Fourier-Transform Infrared (FTIR) study for Algerian asphaltenes

despite that the Algerian light oil contain a few quantity of asphaltenes (under to 0.7 wt %)but The problem of their deposition during the oil production and transportation is strongly suggested, this deposition of asphaltenes does not depend on the percentage of asphaltenes in the oil but depends on their chemical composition which affects the behavior of asphaltenes. Functional Groups of Algerian Asphaltenes was investigated using A Fourier-Transform Infrared (FTIR),This study characterizes a Six samples of asphaltenes were collected from Hassi Messaoud’s oil field at different locations, all samples were extracted using n-heptene with with 1:40 (g/ml) (oil to solvent ratio),the obtained results indicated the existence of aliphatic, aromatic and sulfoxide groups with different intensities. This study confirmed that the asphaltenes precipitation was occurs in all Hassi Messaoud’s oil field locations. Keywords : Asphaltenes; Extraction; Characterization; A Fourier-TransformInfrared (FTIR); Algerian Light oil.

New modified selective platinum electrode based on poly (ethylene glycol) for Iron (III) detection in real water

PurposeThis work aims to determine iron (III) in real water by using a new amperometric sensor on the basis of polyethylene glycol (PEG) to test and characterize a new modified selective platinum electrode.Design/methodology/approachIn this review, the authors focus on testing and characterizing several polymeric membranes by using cyclic voltammetry and square-wave voltammetry (SWV) methods to differentiate the nature of plasticizers (2-Nitrophenyl octyl ether [NPOE], Di-n-octyl phthalate, Bis (2-ethylhexyl) sebacate, PEG. The authors have evaluated the possibility of using crown ether and three zeolite ionophore (faujasite [FAU], Chabazite and ZSM-5) matrixes as novel materials for the selective determination of iron (III) using SWV for the best membranes.FindingsThe results demonstrated that the modified platinum electrode presents linear dependence of amperometric signal with a wide linear range of 10−9 to 10−4 mol.L−1 for iron determination, revealing a detection limit of 10−10 mol.L−1 and amperometric sensibility of 58.58 µA/mol.L−1. The slope of the membrane plasticized with PEG calibration curve is six times higher than that of the other membranes. It was noticed that when the crown ether and the three zeolite ionophores were used, as a new detective material for iron with the membrane plasticized with PEG, the expected results were highly proven. The modified platinum electrode showed high selectivity to iron (III) when the heavy metal ions such as Ni (II), Al (III), Zn (III), Cd (II), Gd (II) and Cu (II) were present.Originality/valueThe utility of the method and the efficiency of the best membrane sensor have been accurately tested by the determination of iron in real water samples of Hassi Messaoud, south of Algeria.

Electrical Energy Generated by Amorphous Silicon Solar Panels

This paper presents studies carried out on amorphous silicon solar panels for electrical power generation in the city of Hassi Messaoud, Ouargla. The electrical power generation has been studied as a function of the amount of irradiation received and the angle of optimum orientation of the solar panels. An optimal angle of 32 degrees is chosen and the amount of solar radiation received is studied. A direct correspondence was observed between the incident solar radiation and the power generated. The maximum variable power is generated between the months of March and October. During the winters, the power generated slows down as the solar radiation available decreases. The power generated by amorphous silicon solar is almost ∼ 20% less than the same generated by the crystalline Silicon solar panels under similar conditions.

Simultaneous inversion application for characterizing Hamra Quartzite tight sand reservoir: a case study from Hassi Messaoud (Algeria)

Channel sand acts as a stratigraphic trap for hydrocarbon accumulation in many parts of the world. Delineation of this type of reservoir is crucial as channel sand may be scarce, and inaccurate location of the drilling wells could lose a huge currency. The Hassi Messaoud (HMD) field was subjected to multiphase tectonic events, where deep-seated structures were rejuvenated leading to intensive fault complexity. The main effective tectonic events upon the studied area are the Hercynian compression and deep erosion till the Ordovician Hamra Quartzite (HQZ) oil reservoir, followed by active Triassic rifting and filling the deeply eroded areas or the graben areas by eruptive volcanic rocks at Triassic time. Hercynian erosion and volcanic rocks distribution introduce a big uncertainty to the reservoir structural model. Amplitude versus offset (AVO) method is used as a helpful tool to differentiate channel sand from surrounding formations. Several attributes (P-impedance, S-impedance, longitudinal velocity Vp, shear velocity Vs and density ρ) are estimated from pre-stack seismic inversion. They have different sensitivity to the reservoir properties. Derived attributes such as Lame parameters, incompressibility × density (λρ) and rigidity × density (μρ) can provide key lithology and fluid indicators (Goodway et al. 1997, Goodway CSEG Rec 26(6):39-60 2001). Petrophysically relating AVO attributes both to λρ and μρ and to each other in Lambda–Mu–Rho (LMR) cross-plot space can be a good tool for AVO interpretation (Rutherford and Williams Geophysics 54:680–688 1989 and Castagna and Swan Lead Edge 16(4):337–342 1997). After proper data conditioning, simultaneous inversion of pre-stack angle gathers is performed to get acoustic wave impedance (P-impedance), elastic wave impedances (S-impedance) and density ρ, then to calculate λρ and μρ volumes. In the studied area, λρ and μρ are used as a very important key to separate reservoir sands. The λρ and μρ curves are generated at each well location. Cross plots showed a fair separation of sand in the formation, i.e. higher μρ and lower λρ can detect sand. The output λρ and μρ volumes after simultaneous inversion follow the distribution of the sand which is consistent with the wells penetrating the target reservoir. This finding on the extension of the sand reservoir in terms of λρ and μρ. 3D cross-plot zonations are used for lithology discrimination. In this study, well logs were used to constrain lithology and to control the zonation filters by reducing the limits ambiguity. Other types of advanced attributes are calculated and tested. The obtained (μρ–λρ) volume acts as a good indicator for the sand distribution. It was finally used as sand presence index in the area. Also μρ has shown a good linear relationship with porosity. To note that the porosity volume is created based on the linear relationship with μρ. A product of derived porosity and the sand presence index (μρ–λρ) provides a good tool for reservoir characterization and lead to reservoir management, future planning of the field, and setting location for new wells.

Groundwater quality in arid regions: The case of Hassi Messaoud Region (se Algeria)

After chemical quality study, it has been realized that the groundwater of Hassi Messaoud region isn’t drinking one according to WHO and Algerian standards for drinking water. This water is highly mineralized and very hard and its major concentrations are often higher than recommended standards, so it requires treatment before use. The time that irrigation water quality is based on riverside standards (1954), the waters of the terminal complex of aquifers have average SAR values high, these waters arrange themselves in the poor and bad classes. However Continental Intercalary waters arrange themselves in the poor classes for irrigation.

State of stress in exhumed basins and implications for fluid flow: insights from the Illizi Basin, Algeria

Abstract The petroleum prospectivity of an exhumed basin is largely dependent on the ability of pre-existing traps to retain oil and gas volumes during and after the exhumation event. Although faults may act as lateral seals in petroleum traps, they may start to become hydraulically conductive again and enable fluid flow and hydrocarbon leakage during fault reactivation. We constrain the present day in situ stresses of the exhumed Illizi Basin in Algeria and demonstrate that the primary north–south and NW–SE (vertical strike-slip) fault systems in the study area are close to critical stress (i.e. an incipient state of shear failure). By contrast, the overpressured and unexhumed Berkine Basin and Hassi Messaoud areas to the north do not appear to be characterized by critical stress conditions. We present conceptual models of stress evolution and demonstrate that a sedimentary basin with benign in situ stresses at maximum burial may change to being characterized by critical stress conditions on existing fault systems during exhumation. These models are supportive of the idea that the breaching of a closed, overpressured system during exhumation of the Illizi Basin may have been a driving mechanism for the regional updip flow of high-salinity formation water within the Ordovician reservoirs during Eocene–Miocene time. This work also has implications for petroleum exploration in exhumed basins. Fault-bounded traps with faults oriented at a high angle to the maximum principal horizontal stress direction in strike-slip or normal faulting stress regimes are more likely to have retained hydrocarbons in exhumed basins than fault-bounded traps with faults that are more optimally oriented for shear failure and therefore have a greater propensity to become critically stressed during exhumation.

Treatment and Reuse of Wastewaters Discharged by Petroleum Industries (HMD/Algeria)

Industrial wastewaters discharged by petroleum industries contains: oil, heavy metals and chemicals used in the process of oil separation and treatment. These waters are a source of soil, water and air pollution, and lead a mortal danger to the ecosystem. Our aim in this work has an aspect that can contribute to the collective effort to address the enormous amount of water purges storage bins and reuse them to avoid any environmental damage. This was achieved by chemical treating of these wastewaters discharged from three different locations of Hassi Messaoud (HMD) petroleum field by flocculation with (C-5563) followed by coagulation with (C-2061) using two different acids as sequestering namely: Ascorbic and Citric acid. After experiments, the results showed that the wastewater can be treated without sequestering by adding 40 ppm of activated silicates. The best result was obtained by addition of 160 ppm of Ascorbic acid as sequestering agent and 20 ppm of activated silicates; resulting in removal of 92.81 % of suspended matter and 95.53 % of turbidity. Finally we concluded that this wastewater was satisfactorily treated and we recommend either inject it for enhanced oil recovery in industrial closest field (North field) to maintain the reservoir pressure and the improved rate recovery of oil reserves or reuse it in garden irrigation. In order to see the impact of the treated water on plants, irrigation tests have conducted on two types of plants (date palm and shaft apocalyptic) for one year. The tests showed that the thick layer of 5 cm and 0.08mm of particles diameter of dune sand removes most of remaining oil. The sand layer that fills the basin surrounding the shaft is removed and replaced every 06 months. So, Dune sand plays the role of natural filter. The garden plants appear and grow normally.