Analysis Of Wells Research Articles

Characteristics of scale deposition in gas-condensate wells

Formulation of the problem. The article deals with one of many possible complications that may occur in the process of gas and gas-condensate wells operation. In fact, scale deposits can be observed in wells at all stages of field development. Scale deposition inside the tubing has a negative impact on hydrocarbons production. This causes the decline of gas production rate. The major factor of scale deposits formation is overtreatment of water solution with different salts and the effect of field hydrogeology. Thus, special methods are used in practice to prevent scale deposition and combat this complication.The purpose of the article. To define the causes of scale deposition, the detailed analysis of well operation should be performed that will help to take the appropriate prevention measures. Methods. The authors’ own achievements as well as the research results of domestic and foreign investigators made the methodical basis for the article.Results. The production data of the wells from different fields have provided the information about scale deposition. Many of the described ways of combating and eliminating scale deposits are expensive, their use causes well downtime and production decline. Therefore, it has been proposed to take easy-to-use preventive measures.Scientific novelty and practical significance. During investigation of the production researches results and calculations the specialists of UkrNDIgas proposed to classify the wells with reduced production capacities within the field into groups and categories according to the degree of total salinity of formation water. It has been proposed to control the process of scale deposition by the results of water analysis, taken from the wells. Each well has the set limit values of salinity.Based on the operation analysis of wells in different fields, the calculated predicted results of scale deposition in wells according to the existing procedures and their comparison with the factual data from production fields, the specialists of the institute have developed the efficient complex multi-faceted measures.

Extensional Messinian basins in the Central Mediterranean (Calabria, Italy): new stratigraphic and tectonic insights

The direction of extension and the architecture of the Messinian basins of the Central Mediterranean region is a controversial issue. By combining original stratigraphic analysis of wells and seismic profiles collected offshore and onshore Calabria, we reassess the tectonic evolution that controlled the sedimentation and basement deformation during Messinian times. Three main deep sedimentary basins in the Calabria area record a Messinian succession formed by two clays/shales-dominated subunits subdivided by a halite-dominated subunit. The correlation with the worldwide recognized stratigraphic features permit to define the chronology of the stratigraphic and tectonic events. Three main rift basins that opened in a N-S direction have been recognized. On the contrary a fourth supradetachment basin opened toward the East. We found that the basin subsidence was controlled by two stages of activity of normal faults and that Messinian rift basins evolve in a deep-water environment. The overall pattern of extensional faults of the Central Mediterranean corresponds to normal faults striking parallel to the trench and normal faults striking at an oblique angle to the trench (Fig. 14). In particular in Campania and Calabria regions are present two rifts parallel to trench and an intervening rift orthogonal to the trench. We maintain that the recognized Messinian rift basins can be interpreted according to the “Double-door saloon tectonics”.

Discussion on “Performance analysis of Wells turbine blades using the entropy generation minimization method” by Shehata, A. S., Saqr, K. M., Xiao, Q., Shahadeh, M. F. and Day, A.

This paper presents a critical appraisal of the paper “Performance analysis of Wells turbine blades using the entropy generation minimization method” by Shehata, A. S., Saqr, K. M., Xiao, Q., Shahadeh, M. F. and Day, A., published in Renewable Energy, volume 86, pp. 1123–1133. The discussion focuses in particular on five aspects of the work being critiqued: the set-up of the numerical experiment, the similarity of the problem studied with the large existing literature on oscillating airfoils, the estimation of entropy generation through the numerical solution of the Navier-Stokes equations, the equivalence between entropy and drag, and finally a comparison of the results presented with existing literature. From this appraisal, it is concluded that the problem studied is not representative of a Wells turbine and that the article contains a number of fundamental errors that lead to incorrect results. These mistakes would have been evident had the results been analyzed critically and compared to the existing literature on the subject. If the results had been presented in non-dimensional form, as best practice recommends, they would have been more readily comparable to those in existing literature and important discrepancies might not have been obscured.

Reply to: Discussion on “performance analysis of wells turbine blades using the entropy generation minimization method” by Shehata, A. S., Saqr, K. M., Xiao, Q., Shahadeh, M. F. and Day, A

Abstract With great interest, the authors have read the comments made by Ghisu et al. on our recent paper [1] published in Renewable Energy. The comments severely criticizes our methodology and results, which actually provide us with fortunate opportunity to discuss our work in more details to complement our work, thankfully to this available space of scientific discourse provided by Renewable Energy editors. In this reply, we show clearly that all the comments proposed by Ghisu et al. lacks sufficient understanding of Wells turbine modeling approaches, literature, and state of the art research practices. We also show that Ghisu et al. could not distinguish between fully developed turbulent flow and transitional flow around Wells turbine airfoils. It is also evidently shown that their concerns about the entropy generation calculation method are meaningless in the light of well-established practices of CFD models of entropy generation minimization principles. Our reply is structured in a point-by-point style to address the comments raised in the discussion article and help the readers understand our work in better details.

The effect of salinity and gas saturation of a geothermal fluid on the reservoir permeability reduction

Highly saline geothermal reservoirs show problems of salt precipitation on the rock formation reducing its permeability and the well’s productivity. In this study, theoretical curves of mass productivity of geothermal wells (inflow type curves) were obtained considering ternary mixtures of H2O-CO2-NaCl of up to 25% salinity in weight and under different initial conditions of gas saturation of the fluid. The sensitivity analysis to the initial concentration of salts and initial gas saturation was carried out using the simulator TOUGH2. The developed type curves are focused to reservoirs with criti-cal characteristics such as, low permeability, ranges of high salt precipitation and high gas saturation. The obtained curves show three clearly defined zones as a function of the degree of exploitation of the well: no salt precipitation zones; transition zones; and salt precipitation zones. It was found that salt precipitation in the reservoir occurs in greater intensity at higher initial concentrations of dissolved salts and higher gas saturation. In some cases, scale obstructs the pores of the rock formation drastically reducing its permeability. It is proposed that type curves could be used as complementary tools for the analysis of wells and for the selection of pertinent strategies for the exploitation of geothermal fields.

Jurassic stratigraphy of the Belluno Basin and Friuli Platform: a perspective on far-field compression in the Adria passive margin

Anomalous patterns of the sedimentary architecture have been recognized in passive margins, and only recently they have been associated with plate reorganization or compressional deformations propagating from distant margins. With the aim of discussing the sedimentary architecture and the potential tectonic perturbations to the passive margin pattern, we present the revision of the stratigraphy of a fossil passive margin, involved in the retrobelt of the Alpine orogeny. The main events at the transition from rifted to passive margin have been controlled by palaeoceanography, i.e. the trophic state of surface waters that hampered the carbonate photozoan productivity for a long period between Toarcian and Callovian. Toward the latest Bajocian–earliest Bathonian, the platform productivity increased, dominated by ooids. A regressional trend up to the Middle Bathonian allowed the rapid infilling of the previous rift basin. The successive aggradation in the platform was still dominated by non-skeletal grains until the Early Oxfordian. The Middle Oxfordian to Early Kimmeridgian was a time of recovery of the palaeoceanographic conditions allowing the establishment of a hydrozoan/coral rich platform. The sedimentation rates in the platform increased at the margin of the productive Friuli–Adriatic Platform. From Late Kimmeridgian on, the sedimentation rates at the platform margin returned to the pre-Oxfordian values. At the scale of the whole Adriatic Platform, the Middle Oxfordian to Early Kimmeridgian interval is variable in thickness from 0 to 800 m, and it depicts a couple of folds of around 80–100 km of wavelength. The subsidence analysis of wells and composite logs from literature suggests this interval as a perturbation to the passive margin trend of around 3 Myr of duration. We interpret this folding event, superimposed to the passive margin subsidence, as the far field expression of the transition from intraoceanic to continental obduction, occurred at the eastern Adria active margin.

A Comparative Analysis of Wellness in Adulthood Based on High School Athletic Participation

A Comparative Analysis of Wellness in Adulthood Based on High School Athletic Participation

Pressure buildup test analysis in wells with sustained casing pressure

When the well's casing head pressure cannot be permanently bled off with a needle valve, the casing is said to exhibit Sustained Casing Pressure (SCP). Rebuilding of surface pressure (pressure buildup – after closing the valve) results from migration of gas in the leaking cement sheath of the well's annulus. Problem of sustained casing pressure (SCP) has been widespread in the Gulf of Mexico and also reported in Canada, Norway, and other places. Regulations require 24-hr testing of SCP wells comprising pressure bleed-down followed with pressure buildup. In these tests, the rate of pressure buildup is indicative of the size of cement leak – prompt buildup implies larger leak on a relative scale with no quantification. Presented here is the first mathematical model for quantitative analysis of pressure buildup in SCP wells. The model simplifies transient gas flow in cement and ignores migration time of gas in the annular fluid column above the cement top. The simplification allows finding the size of cement leak and the depth and value of gas pressure source formation.Also presented is validation of the model with actual field data from testing SCP wells. Matching the model to field data gives acceptable estimates of the gas-source formation depth and pressure, cement leak size, and expected maximum casing pressure value. The results also reveal a correlation between the pressure buildup-stabilization pattern and well parameters - cement leak size controls the pressure buildup rate, while the gas-source formation pressure controls the stabilized pressure value. Quantitative analysis of SCP buildup with the new model could be extremely useful as it provides values of three parameters (cement leak size, gas source formation depth and pressure) that are critically important for designing remedial treatment.

Seismic and Sequence Stratigraphic Analysis of Ewan and Oloye Fields (Middle Miocene), Northwestern Niger Delta: Implications for Deltaic Depositional Sequences

The main aim of this works is to define local sequence variability and its implications for deltaic depositional sequences within the studied area. This research work makes use of depth converted three dimensional seismic cube, well logs, core photography descriptions and biostratigraphic reports. Recognition and interpretation of stratal surfaces were based on facies shifts and stacking patterns and reflection terminations derived from the interpretation of seismic data and wireline logs integrated with core photography and biostratigraphic reports. Seismic stratigraphic analysis of well and seismic data suggests that middle Miocene- early Pliocene strata within the studied area were made of six depositional sequences. Sequences are made up aggradational to progradational HST that makes up about 50% of a sequence. TST are thin and widespread while LST are restricted to within WNWESE trending valley fills typically 4 km wide and an average 120 m deep. Outside the LST valleys, transgressive surfaces, maximum flooding surfaces and sequence boundaries are coincident on interfluves. This suggests that during LST times most of the area was periodically subaerially exposed and several incised valleys/canyons were developed. These incisions/canyons acted as a sand feeder that led to the deposition of high amplitude deposits (sandstones) on the slope and within the basin floor setting. Sequences mapped over the study area show local variation associated with growth faults. There is a strong local growth fault control on sequence variability. Further local controls on sequence geometry are shelf instability and slope scars which have a strong geomorphological impact on the area. The depth of incised valleys within the uppermost HST (up to 350 m) is difficult to explain in terms of sea level fall alone because eustatically-driven sea level variations during the Miocene are generally reported to be less than 100 m (330 ft). This suggests that the character of sequence development and depositional facies preserved within the study area depends on relative sea level changes, relative rates of regional structural collapse and sedimentation rate. The occurrence of several incisions in the middle Miocene succession is interpreted as evidence of significant relative sea level fluctuations, and the presence of type-1 sequence boundaries may be the stratigraphic signature of major drops in relative sea level during Miocene and Pliocene. Variability within the depositional sequences is said to be largely controlled by local growth faults, rapid relative sea level changes, basin physiography (shelf edge) and high rate of sediment influx.

Investigation on flow regimes and non-Darcy effect in pressure test analysis of horizontal gas wells

Abstract Transient pressure test of horizontal wells compared to vertical wells is more complicated due to the occurrence potential of different transient flow periods. Although various mathematical models were developed for horizontal well test analysis their evaluation in different well and reservoir conditions needs more investigation. In specific, in vertical wells non-Darcy flow which causes an extra pressure drop, has a significant impact on well test data but its impact on horizontal well test data needs more investigation. The objective of this paper is to examine transient pressure behavior of horizontal gas wells under various conditions including high velocity flow. For this purpose, a horizontal gas well in a finite rectangular reservoir with typical geometry is simulated using a commercial reservoir simulator. Synthetic well data are used to plot pseudo-pressure derivative curves which identify appeared flow regimes. Sensitivity study is done considering relative well lengths and well location with respect to horizontal boundaries as well as non-Darcy flow parameter. The results show that the appearance of elliptical and pseudo-radial flow regimes depends on relative well length and formation thickness. In addition, the effect of off-centered wells with respect to upper and lower boundaries in transient pressure data is expressed. The results also show that non-Darcy flow can cause a significant skin in transient data of a horizontal gas well. Magnitude of the skin is mainly affected by reservoir permeability and production rate of the horizontal well. Contrary to the general belief regarding negligible effect of non-Darcy flow in analysis of horizontal gas well test, this study showed that it can cause a significant error in analysis of the well test data.

Assessment of Hydrological Properties and Proximate Impact of Septic Tank Leachate on Well-water Quality in Two Residential Areas in Ibadan, South-western Nigeria

Aims: To determine the impact of leachate from septic tank on proximate well - w ater quality in two different residential areas and the variation in the physico - chemical parameters of the well - water that are associated with spatial geographical location. Study Design : Randomized monthly collection and analysis of well - water over four months in two chosen residential areas. Place and Duration of Study: Residential houses at Agbowo and Akobo, Ibadan, Nigeria between April and August, 2012. Original Research Article

The chemical characterization of the thermal waters in Budapest, Hungary by using multivariate exploratory techniques

Europe’s largest naturally flowing thermal water system can be found in Budapest, Hungary. The thermal waters are used mainly for balneological purposes, and hence a huge database is available about the chemical status of these waters at the bath company. This study has been prepared with the purpose of characterizing the chemical composition of the thermal waters of Budapest through descriptive statistics and multivariate exploratory techniques. A further objective was to determine the factors influencing the physico-chemical parameters and to investigate the temporal changes in water quality. The characterization was based on a database containing regular quarterly water chemical analyses of wells and springs collected over several decades (1960–2009).

Abstract 2339: Transcriptional basis for loss of cellular differentiation in colon cancer

Abstract Background: Colon cancer is a leading cause of cancer related death. Colon cancer arises due to uncontrolled cell proliferation, failure of cells to undergo apoptosis and loss of cellular differentiation. While the pathways which drive the uncontrolled proliferation of colon cancer cells are relatively well understood, the mechanistic basis for loss of cell differentiation is less well characterized. The aim of this study was to identify novel transcription factors that regulate the differentiation status of colon cancer cells. Methods: Affymetrix microarrays were used to identify transcription factors which are significantly differentially expressed between well differentiated and poorly differentiated colon cancer cell lines. Differential gene expression was confirmed by q-RT-PCR in 40 colon cancer cell lines. The well differentiated colon cancer cell line SW948 was transfected with siRNAs using lipofectamine. Results: Microarray analysis of well and poorly differentiated colon cancer cell lines identified the EHF transcription factor to be significantly downregulated in expression in poorly differentiated cell lines. Q-RT-PCR analysis demonstrated that while both EHF variants were expressed in a panel of 40 colon cancer cells, variant 2 was the isoform differentially expressed between well and poorly differentiated cell lines. Basal expression of EHF correlated significantly with expression of the differentiation markers villin and KRT20 across the 40 cell line panel. Knockdown of EHF in the well differentiated colon cancer cell line SW948, reduced expression of villin and KRT20 by 82% and 64% respectively. Knockdown of EHF also reduces expression of Cdx1 suggesting it may be act upstream of this known differentiation regulator. Conclusion: This study identifies the transcription factor EHF as a novel regulator of cell differentiation in colon cancer. Citation Format: Ian Y. Luk, Hoanh Tran, Janson WT Tse, Anderly C. Chueh, Fiona Chionh, Nicholas J. Clemons, John M. Mariadason. Transcriptional basis for loss of cellular differentiation in colon cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2339. doi:10.1158/1538-7445.AM2014-2339

Gas-Production-Data Analysis of Variable-Pressure-Drawdown/Variable-Rate Systems: A Density-Based Approach

Summary This study demonstrates that production-data analysis of variable-bottomhole-flowing-pressure/variable-rate gas wells under boundary-dominated flow (BDF) is possible by use of a density-based approach. In this approach, governing equations are expressed in terms of density variables and dimensionless viscosity/compressibility ratios. Previously, the methodology was successfully used to derive rescaled exponential models for gas-rate-decline analysis of wells primarily producing at constant bottomhole pressure (Ayala and Ye 2013a, b; Ayala and Zhang 2013; Ye and Ayala 2013; Zhang and Ayala 2014). For the case of natural-gas systems experiencing BDF, gas-well-performance analysis has been made largely possible by invoking the concepts of pseudotime, normalized pseudotime, or material-balance pseudotime. The density-based methodology rigorously derived in this study, however, does not use any type of pseudotime calculations, even for variable-rate/variable-pressure-drawdown cases. The methodology enables straightforward original-gas-in-place calculations and gas-well-performance forecasting by means of type curves or straight-line analysis. A number of field and numerical case studies are presented to showcase the capabilities of the proposed approach.

Early-stage rifting of the Southern Tyrrhenian region: The Calabria–Sardinia breakup

The Southern Tyrrhenian Sea is an extensional basins linked to the Neogene evolution of the Calabria subduction zone located in the western Mediterranean realm where controversial kinematic and geodynamical models have been proposed. Our study provides a key to unravel timing and mode of extension of the upper plate and the breakup of Calabria from Sardinia. By combining original stratigraphic analysis of wells and seismic profiles off Calabria with a stratigraphic correlation to onshore outcrops, we re-assess the tectonic evolution that controlled the sedimentation and basement deformation of the Southern Tyrrhenian basin during Serravallian–Tortonian times. We document the tectono-stratigraphic evolution of adjacent extensional basins characterized by 3rd order depositional sequences (Ser1, Tor1 and Tor2) and different modes of extension, subsidence and opposite dipping faults. Episodic basin development is recorded by a coarsening-up and fining-up trend of the sedimentary succession and by tectonically enhanced unconformities that reflect three episodes of fault activity. We reconstruct Serravallian–Tortonian paleogeographic maps and propose a block faulting model for the evolution of the Sardinia–Calabria area. Sardinia was disconnected from Calabria through N–S normal faults forming Tyrrhenian extensional basins that formed contemporaneously to the E–W opening of the Algerian basin. Unlike published Serravallian–Tortonian reconstructions of the western Mediterranean realm, our results support a geodynamic model characterized by rapid trench retreat, trench-normal extension in the entire overriding plate and very weak coupling between plates.

Coal bed reservoir simulation with geostatistical property realizations for simultaneous multi-well production history matching: A case study from Illinois Basin, Indiana, USA

Coal seam degasification is a means to recover energy from the methane gas retained in coal, and is also a supplementary measure to ventilation, which is proven to be one of the most effective ways to reduce methane emissions to a safe level in coal mines. Reservoir simulation is probably the most effective way to assess the coal seam as a “gas reservoir” and thereby its fluid-storage and flow-related properties. This objective is achieved by taking advantage of history matching of wellbore production.Reservoir simulation with multi-well history matching is a tedious process as important coal properties that affect wells' production characteristics are spatially variable across the seam. The common practice is to change various properties at the well blocks during the history matching process, and assume that they are uniform across the domain of interest. This process, however, often does not produce realistic and effective results for well or coal reservoir management. In this work, a multi-level approach to coal bed reservoir simulation is demonstrated for a group of coalbed methane wells in the Illinois Basin producing from the Seelyville Coal Member of the Linton Formation of the Carbondale Group (Pennsylvanian) in Indiana. This approach includes, in order, gas and water deliverability analyses of wells, geostatistical simulation and co-simulation, and coal bed reservoir simulation. It is shown that a reservoir model, which utilizes the geostatistical maps of important coal properties, is effective for simultaneous history matching of all wells, and eliminates the need for guessing and changing values of coal properties at and around individual well blocks. This methodology also provides realistic distributions of reservoir parameters and how they change during gas depletion, and thus aids in coal seam and coal gas management.

Determination of Fluoride in Rural Parts of Kapadwanj Region, District Kheda, Gujarat

Analysis of well and bore well water samples for fluoride from eighteen sampling stations of Kapadwanj(Rural area) for a period of one year( 2012) during different seasons has been carried out. The analysis of different parameters namely- temperature, pHTDS and Fluoride was carried out as per standard methods. The results were compared with the values stipulated by Indian standards for drinking water . It was found that the fluoride content of all the samples obtained was well below the permissible limits.

Transient Pressure Analysis of Wells Intercepted by Partially Penetrating Finite Conductivity Hydraulic Fractures

Most current pressure transient analysis techniques of hydraulically fractured wells are based on the fully penetrating assumption, which assumes equal thickness of hydraulic fracture and the formation. However, field application show that the fractures thickness can be shorter than the thickness of formation, which leads to vertical flow into the fracture. Thus applying the thickness equality assumption of current well test models to a partial penetrating fracture may give contradictory result. Further, there are very few studies concerning pressure transient analysis of partial penetrated wells. So it is important to develop analysis model and procedure to this type of fracture. In this paper, we presented an analytical model for partially penetrating hydraulic fracture in isotropic systems, along with the assumption that fracture is finite conductive. This model is then applied in the analysis of field production data, which verified validity of this new model.

Impact of geologic setting on the groundwater occurrence in wadis El Sanab, Hashem, and Khrega using geoelectrical methods—northwestern coast, Egypt

The present study deals with the complex relationships between the geomorphology and the condition of the groundwater occurrence of three different wadis along the northwestern coastal zone of Egypt in order to provide water for supplementary irrigation and water supply. From the measurements of the geoelectrical techniques (1D and 2D), it is clear that the upstream of wadi El Sanab at the plateau is a promising area where the salinity of drilled well is 2,752 ppm at vertical electrical sounding (VES) no. 1. The delta exhibits lateral facies change that affects the quality of groundwater, and it is clear from the results of water sample analysis of wells. According to the values of resistivity at wadi Hashem, it can be predicted the presence of water-bearing layer may be the third and the last layers. The fifth geoelectrical layer acts as a water-bearing fractured limestone at wadi Khrega, but the potentiality of groundwater is low due to increased clay content that causes low permeability and more salinity in groundwater. Finally, the best side for drilling water wells is in wadi Hashem at VES no. 2 with a depth greater than 75 m. and at wadi Khrega at VES no. 4 with a depth of 70 m. Detecting the save yield for drilled wells is important at wadi El Sanab, especially to maintain the quantity and quality of the groundwater for a long period.

Methodologies for analysis of productivity decline: A review and application

This work emphasizes the convenience of combining several methodologies to assess decline analysis in wells. We show that using different techniques, the reservoir characterization diagnoses are reinforced. Four of the different methods associated to decline analysis in well productivity are shown. The governing equations, used in methodologies of analysis decline, normalized flow and increase of the damage effect, were reviewed. The diagnosis applied to identify the decline model type, using the classical methodology of analysis, was shown. The comparison between predicted and measured values using normalized flow methodology provides reliable results. Through determining the damage effect technique it was found a direct correlation between the productivity decline and the increase in damage value along the productive life of the well. Geochemical variations in fluids can also provide support in decline rate studies of wells. The methodologies reviewed in this work help in looking for integral solutions to improve the reservoirs productivity.