Test Interpretation Methods Research Articles

Correlation of Consolidation Parameters of Cohesive Soils with Piezocone Penetration Test Data

This paper presents an evaluation of the piezocone penetration test (PCPT) interpretation methods and the development of new correlation methods for reasonably estimating the consolidation parameters of cohesive soils, namely, the constrained modulus and overconsolidation ratio (OCR). Laboratory and in situ PCPT test data collected from seven sites in Louisiana were used in this study. Shelby tube samples were collected and used to evaluate the consolidation properties in a laboratory. Statistical analyses were conducted to evaluate the current interpretation methods and to explore new correlations. The results of this study showed that the PCPT data can be reasonably implemented to calculate the constrained modulus and OCR of cohesive soils. Backcalculated constrained modulus and OCR parameters from field measurements are in close agreement with PCPT-derived values.

EVALUATION OF MEASURED AND INTERPRETED FAILURE LOADS OF BORED PILES IN ALLUVIAL SOIL DEPOSITS

ABSRTACT: This paper presents an evaluation of the ultimate load carrying capacity of bored piles measured directly and obtained from selected methods of load test data interpretation based on different failure criteria. Large scale bored piles were installed in alluvial soil deposits and statically loaded to failure. The measured failure loads varied from 195 to 520kN and pile displacements of 1.3 to 2.7%D were required to mobilize such loads for the considered test conditions. The pile shaft friction component contributed over 83% of the total measured ultimate capacity and was fully mobilized at displacements of 0.2 to 0.8%D. A rigorous analysis was carried out to compare the measured and interpreted pile failure loads and evaluate the performance of six published load test interpretation methods. Based on the evaluation results, the L1-L2 and the Fuller and Hoy’s interpretation methods indicated the best overall performance in estimating the failure loads. The De Beer and Van der Veen methods revealed similar and fairly good evaluation ratings whereas the Davisson interpretation method showed a relatively poor performance. The Chin’s method exhibited a gross overestimation of measured ultimate capacities and among all yielded the poorest overall performance.

Well testing interpretation method and application in triple-layer reservoirs by polymer flooding

Well testing method has historically been the main source of formation evaluation in oilfields. This work demonstrates well testing analysis for formation evaluation in crossflow triple-layer reservoirs by polymer flooding, and a well testing model is proposed by considering mechanical degradation, dispersion, convection, and shear-thinning of polymer solutions. The type curves, having five segments with different flow regime, are developed based on this model, and parameter sensitivity is analyzed. The typical characteristic is the existence of two ’concaves’ in the type curves, distinguished from one-layer and double-layer reservoirs. A field test validates the proposed well testing model, which can effectively evaluate the layered permeability and skin factor. Furthermore, formation damage due to adsorption of polymers at the rock surface is estimated through comparison of the interpreted parameters with the values prior to polymer flooding, which explores the feasibility of applying this interpretation method in formation evaluation of polymer flooding reservoirs.

Investigation on Actuating Pressure Gradient of Low Permeability Reservoir

Due to the presence of actuating pressure of low permeability reservoir, researching on actuating pressure gradient of low permeability reservoir is necessary. While actuating pressure gradient is relevant to permeability and porosity, it can be obtained through laboratory experiments, well testing interpretation method and theory derivation combined with practical application method. The results of a large number of laboratory experiments show that actuating pressure is related to permeability. The greater the permeability is, the smaller the actuating pressure is. They both present the similar hyperbolic relationship; the greater the viscosity of the oil is, the greater the actuating pressure is. Here, we get the actuating pressure gradient formula through the method of theory derivation combined with practical application, meanwhile we put forward the relationship between actuating pressure gradient and permeability, porosity and viscosity. Key words: Low permeability reservoir; Actuating pressure gradient; Porosity; Fluid viscosity

A piezocone dissipation test interpretation method for hydraulic conductivity of soft clays

An alternative approach is developed in order to estimate the hydraulic conductivity of soft fine grained soils, based on numerical simulation of the full penetration and dissipation process for piezocones. Unlike previous methods of analysis, the process of penetration and dissipation has been explicitly simulated, thus eliminating several of the simplifications inherent in existing interpretation methods such as geometric approximations, predefined stress fields or neglecting material compressibility. The presented method is not established upon a particular set of data leading to limited applicability, but is rather developed using a more general approach and can be extended to other datasets if intended. Given the time to 50% consolidation and a number of influencing soil parameters, a single estimate of the soil horizontal permeability can be obtained via a single-run piezocone sounding using pore pressure measurements taken at the shoulder filter element (u2) located immediately behind the cone.The proposed interpretation method embodies many of the key parameters (namely the soil shear strength, soil rigidity, and soil confining stresses) likely to influence the soil behaviour and thus the parameter to be interpreted. Numerical analyses demonstrated that the rate of dissipation increases as the soil rigidity or the soil confining pressure increases, which is a consequence of higher excess pore pressure gradient at higher depths or at larger rigidities. The method, which involves a new excess pore pressure normalisation technique, is applicable to both monotonic and dilative dissipation data. The proposed interpretation method is compared to a series of experimental data including two recent field tests. Although the method was calibrated against only a select few cases, its applicability to a wide range of clayey soils was verified.

Research on Starting Pressure Gradient of Low Permeability Reservoir

Due to the presence of starting pressure of low permeability reservoir, so researching on starting pressure gradient of low permeability reservoir is necessary. while starting pressure gradient is relevant to permeability and porosity, it can be obtained through laboratory experiments¡¢well testing interpretation method¡¢theory derivation combined with practical application method . The result of a large number of laboratory experiments shows: starting pressure is related to permeability .The greater the permeability is, the smaller the starting pressure is. They both present the similar hyperbolic relationship; the greater the viscosity of the oil is, the greater the starting pressure is. In this paper, we get the starting pressure gradient formula through the method of theory derivation combined with practical application, meanwhile we put forward the relationship between starting pressure gradient and permeability, porosity¡¢viscosity .

Numerical Well Testing Interpretation Method of Composite Model and Applications in Offshore Reservoirs by Polymer Flood

Numerical Well Testing Interpretation Method of Composite Model and Applications in Offshore Reservoirs by Polymer Flood

Evaluation of the inter-porosity exchange coefficient inferred from well test in a fractured reservoir with a non-uniform distribution pattern: A numerical study

Characterisation of the fractured reservoirs is of great importance as reservoirs of this type represent a significant proportion of the aquifers and petroleum reservoirs in the world. Well test is one of the main tools for this purpose. Inter-porosity fluid exchange coefficient is one of the parameters that should be determined in this kind of reservoirs as a result of well test. This paper investigates the inter-porosity fluid exchange coefficient inferred from well test in non-uniformly distributed fractured reservoirs through numerical fracture network and flow modelling. Here, we examine the impact of the fracture distribution and pumping well location on the reservoir hydrodynamic response during a well test by numerical simulation. To do so, several synthetic fractured models are prepared by use of a commercial geo-modeller. Numerous well tests are simulated in these models and their hydrodynamic responses to the pumping well are recorded and interpreted applying classical methods of well test interpretation in fractured reservoirs. Finally the inferred inter-porosity fluid exchange coefficients are compared; it is shown that, in a non-uniformly fractured system, this coefficient value is highly dependent on the fracture distribution pattern, pumping well location and its connectivity to the flow-path network. Consequently, we demonstrate that the standard and classic methods of the average matrix bock dimension estimation by well test may be very sensitive to the pattern of fracture distribution (uniform or non-uniform). • Inter-porosity fluid exchange coefficient inferred from well test is studied. • It is done in non-uniformly distributed fractured reservoirs by numerical simulation. • This coefficient value is highly dependent on the fracture distribution pattern. • It is relative to pumping well location and its connectivity to flow-path network.

Well Test Interpretation Method of Horizontal Well in Stress-Sensitive Gas Reservoir

Stress-sensitive widely exists in fractured reservoir. In this paper, a mathematical model of flow in stress-sensitive reservoir with horizontal well is established based on experimental data and with process of linearization. By using of Lord Kelvin point-source solution, Bessel function integration and Poisson superimpose formula, the dimensionless pressure response function of horizontal well in infinite stress-sensitive reservoir is obtained. And then the derivative type curve is calculated. Based on the type curve, the characteristics and influencing factors of the fluid flow through porous medium of horizontal well in stress-sensitive gas reservoir are analyzed.

Clinical significance of the mixing test in laboratory diagnoses of lupus anticoagulant

The mixing test is used to determine the presence of inhibitors in laboratory diagnoses of lupus anticoagulant. Updated international guidelines state that an integrated lupus anticoagulant test system does not require the mixing test; an appraisal of the mixing tests in integrated lupus anticoagulant test systems is, therefore, required. We investigated the clinical relevance of mixing tests by using the best cutoff value of the mixing test through thrombotic risk analysis. A retrospective analysis was performed on 525 specimens with positive screening tests by using two integrated lupus anticoagulant tests: diluted Russell's Viper venom (dRVVT) and silica clotting time. The diagnostic performance of two interpretation formulas (percentage correction, Rosner index) was assessed, and the thrombotic risk of a subgroup based on the mixing results was investigated. Finally, the thrombotic risk of lupus anticoagulant positivity based on the integrated lupus anticoagulant test system procedures was assessed for the appraisal of mixing test exclusion in integrated lupus anticoagulant test systems. The best cutoff values of mixing test interpretation methods based on dRVVT were as follows: 60.1% for percentage correction and 15.7 for Rosner index. There was no substantial difference in the thrombotic risk between percentage correction and the Rosner index. The mixing-positive group showed a higher lupus anticoagulant titer and higher thrombotic risk than the mixing-negative group. However, even the mixing-negative group carried a significant risk of thrombosis. Finally, lupus anticoagulant positivity determined by the updated two-step procedure (screening and confirmation tests) showed higher thrombotic risk than that determined by the traditional three-step procedure (screening, mixing, and confirmation tests). Although a positive mixing result can predict a high risk of thrombosis, negative mixing results are also associated with a substantial thrombotic risk. The updated two-step procedure without the mixing test is relevant for lupus anticoagulant detection in the context of thrombotic risk estimation.

Borehole resistance and vertical temperature profiles in coaxial borehole heat exchangers

Ground source heat pump systems are often coupled to the ground by circulating a fluid through vertical Borehole Heat Exchangers (BHEs). The design of a system requires estimates of the ground thermal conductivity and the borehole thermal resistance, which are usually determined by an in situ thermal response test on a completed borehole. The usual test interpretation methods average the inlet and outlet fluid temperatures and use this mean temperature as the average temperature along the borehole length. This assumption is convenient but does not strictly apply. For a coaxial heat exchanger this paper develops an analytical model for the vertical temperature profiles, which can be used instead of the mean temperature approximation to estimate borehole resistance. The model is verified with measured temperatures on a BHE, where an optical technique allows continuous measurements along a coaxial borehole during a distributed thermal response test. A sensitivity study shows that the proposed method corrects errors in the mean temperature approximation, which overestimates the borehole resistance in a coaxial borehole.

Groundwater resources assessment for irrigable agricultural lands in the Wadi Araba area, southern Jordan

The main target of this research paper was to the hydrogeological assessment of the groundwater resources to irrigate 600 ha of irrigable agricultural lands, distributed along the Dead Sea–Aqaba Highway in Umm, Methla, Wadi Musa, Qa’ Saideen and Rahma, southern Jordan. Therefore, a comprehensive groundwater study was commenced by drilling eight new wells which can be used to supply irrigable areas with the existing groundwater that would be enriched by the yield of three proposed recharge dams on Wadi Musa, Wadi Abu-Burqa, and Wadi Rahma. The evaluation of the pumping test data of the drilled was carried out using the standard methods of pumping test interpretation. This was based on the available water table measurements at well locations and knowledge of water flow in the general. The sustainable yield of each well was calculated based on the pumping test parameters. The obtained results indicate that pumping out of Beer Mathkor wells should not exceed 1,100 m3/day in the case of continuous pumping and 8,700 m3/day in the case of intermittent pumping. Since the water table did not significantly change with small changes in pumping (it took eightfolds of magnitude increase in pumping from approximately 1,100 to 8,700 m3/day to show a significant drop in the water table equivalent to about 5.5 MCM per year from the aquifer.

Prediction of Key Points of Water-oil Relative Permeability Curves Using the Linear Regression Technique

Relative permeability is among the most critical parameters in reservoir performance evaluation and EOR projects. It reflects the ease of movement and trapping of different phases and affects the production rate and ultimate recovery from reservoirs. Experimental measurement of relative permeability curves is complicated, costly, time consuming, and the results can easily be influenced by test conditions and interpretation methods. Empirical correlations are alternative approaches that are based on existing experimentally measured relative permeability curves and rock and fluid properties. The authors used 260 relative permeability curves from Iranian carbonate and sandstone reservoirs. Six key points for each set of water-oil relative permeability were determined, which fully characterize these curves. Using linear regression technique, new correlations were proposed to predict these key points. Having this done, it is then easy and straightforward to construct unnormalized/real water-oil relative permeability curves.

Application of Pressure-Rate Deconvolution to Well Test Interpretation of Low Permeability Reservoirs

Pressure-rate deconvolution method based on the newly robust solution algorithm is applied to low permeability reservoirs, and deconvolution codes were developed for the study based on Schreoter deconvolution algorithm in this paper. The application of this method in a low permeability oilfield shows that deconvolution can provide much more information than the conventional well test interpretation methods, and this deconvolution method can interpret the whole test sequence but doesn’t be limited in pressure build-up period. It is proved that the pressure-rate deconvolution algorithm works well in well test interpretation of low permeability reservoirs.

A Review of Standardized Tests of Nonverbal Oral and Speech Motor Performance in Children

To review the content and psychometric characteristics of 6 published tests currently available to aid in the study, diagnosis, and treatment of motor speech disorders in children. We compared the content of the 6 tests and critically evaluated the degree to which important psychometric characteristics support the tests' use for their defined purposes. The tests varied considerably in content and methods of test interpretation. Few of the tests documented efforts to support reliability and validity for their intended purposes, often when relevant information was probably available during the test's development. Problems with the reviewed tests appear related to overly broad plans for test development and inadequate attention to relevant psychometric principles during the development process. Recommendations are offered for future test revisions and development efforts that can benefit from recent research in test development and in pediatric motor speech disorders.

Evaluating Deformation Modulus of Cohesive Soils from Piezocone Penetration Test for Consolidation Settlement

The piezocone penetration test (PCPT) interpretation methods were evaluated for reasonable prediction of the deformation constrained modulus (M), which is needed to calculate the consolidation settlement of cohesive soil. Seven sites in Louisiana were selected for this study. In each site, PCPT tests were performed, and soundings of cone tip resistance (qc), sleeve friction (fs), and pore pressures (u1 and u2) were recorded. Dissipation tests were conducted at prespecified penetration depths and used to estimate the vertical coefficient of consolidation (cv) using the Teh and Houlsby interpretation method. High-quality Shelby tube samples were collected close to the PCPT tests and used to carry out a laboratory testing program, including consolidated undrained triaxial tests and one-dimensional consolidation tests. The constrained modulus (M) values predicted by using the different interpretation methods were compared with the reference values determined from the laboratory consolidation tests. Results of this study showed that the Sanglerat method was able to predict Mbetter than the other methods. Two correlations were also developed to predict M from the corrected cone tip resistance (qt) and the net cone tip resistance (qt - σvo). The results of this study were verified by comparing the predicted total and time rate of settlements estimated from piezocone penetration and dissipation data with the laboratory-calculated and field-measured settlements for three selected sites.

Application of TDS technique to developed reservoirs

Conventional well test interpretation methods for a single well in an infinite reservoir may not be suitable in cases where the tested well is affected by other wells operating in the same reservoir. This effect becomes more significant as both the flow rate and the test duration increase. It is observed in drawdown tests when the well experiences an additional pressure decline due to production from other wells and, also, when the well produces under pseudosteady state before shut-in it for a buildup test. When pressure data are interpreted as recorded, estimation of reservoir parameters may not be accurate. Slider 1–3 introduced a technique for analyzing a pressure test that takes into account the effect of nearby active wells. Corrected or extrapolated pressures are obtained by applying the superposition principle to include the pressure decline contribution from the neighboring wells. Traditional semilog plots are then constructed and permeability and skin factor can be estimated, respectively, from the slope and intercept of their linear trend. A new technique, called TDS (Tiab's Direct Synthesis), was designed to analyze pressure and pressure derivative data without using type-curve matching. It uses characteristic features found on the derivative plot, so reservoir parameters are directly estimated. It depends upon how well the pressure derivative is calculated. If derivative is taken to the recorded pressure data the resulting curve will not be properly defined and the estimated parameters may be erroneous. Application of the TDS technique to wells in depleted reservoirs is presented here. The recorded pressure is extrapolated to include the contribution from other wells as suggested by Slider. First, the recorded pressure is extrapolated/corrected to include the contribution from other wells, then the pressure derivative is taken. The TDS technique can now be readily applied. It was successfully tested with synthetic and field examples. A comparative analysis was carried out to see the effects when derivative is taken to uncorrected pressure data and the estimation of permeability, skin factor and drainage area. Two main conclusions are drawn from this study: (1) Using uncorrected pressure data will lead to a significant undersestimation of the drainage area, and (2) Only minor to negligible error in permeability and skin is obtained when the recorded pressure is corrected.

Application of TDS technique to developed reservoirs

Well test interpretation methods for a single well in infinite reservoirs may not be suitable for those wells when their pressure is affected by other wells operating in the same reservoir. This effect becomes more significant as both the flow rate and the test duration increase. It is observed in drawdown tests when the well experiences an additional pressure decline due to production from other wells and, also, when the well produces under pseudosteady state before shut-in it for a buildup test. When pressure data are interpreted as recorded, estimation of reservoir parameters may not be accurate. Slider1–3 introduced a technique for analyzing a pressure test that takes into account the effect of nearby active wells. Corrected or extrapolated pressures are obtained by applying the superposition principle to include the pressure decline contribution from the neighboring wells. Traditional semilog plots are then constructed and permeability and skin factor can be estimated, respectively, from the slope and intercept of their linear trend. A new technique, called TDS (Tiab's Direct Synthesis), was designed to analyze pressure and pressure derivative data without using type-curve matching. It uses characteristic features found on the derivative plot, so reservoir parameters are directly estimated. It depends upon how well the pressure derivative is calculated. If derivative is taken to the recorded pressure data the resulting curve will not be properly defined and the estimated parameters may be erroneous. Application of the TDS technique to wells in depleted reservoirs is presented here. The recorded pressure is extrapolated to include the contribution from other wells as suggested by Slider. Once the pressure derivative of the extrapolated data is taken, the TDS technique as discussed by Tiab [Tiab, D. 1993. Analysis of Pressure and Pressure Derivative without Type-Curve Matching: 1- Factor de daño and Wellbore Storage. J. Pet. Sci. Eng. 12 (1995), 171–181.] can be readily applied. It was successfully tested with synthetic and field examples. A comparative analysis was carried out to see the effects when derivative is taken to uncorrected pressure data and the estimation of permeability, skin factor and drainage area.

Reliability of Piezocone Penetration Test Methods for Estimating the Coefficient of Consolidation of Cohesive Soils

The current piezocone penetration test (PCPT) interpretation methods were evaluated for their capability to estimate the vertical coefficient of consolidation (cv) of cohesive soils reasonably by using the piezocone dissipation tests. Seven PCPT methods were evaluated. Six sites in Louisiana were selected for this study. At each site, in situ PCPT tests were performed, and soundings of cone tip resistance, sleeve friction, and pore pressures at different locations were recorded. Piezocone dissipation tests also were conducted at different penetration depths. High-quality Shelby tube samples were collected close to the PCPT tests and were used to carry out a comprehensive laboratory testing program. The (cv) values predicted by the different interpretation methods were compared with the reference values determined from the oedometer laboratory tests. The results of this study showed that two methods can estimate cvbetter than the other prediction methods.

Reliability of Piezocone Penetration Test Methods for Estimating the Coefficient of Consolidation of Cohesive Soils

The current piezocone penetration test (PCPT) interpretation methods were evaluated for their capability to estimate the vertical coefficient of consolidation (cv) of cohesive soils reasonably by using the piezocone dissipation tests. Seven PCPT methods were evaluated. Six sites in Louisiana were selected for this study. At each site, in situ PCPT tests were performed, and soundings of cone tip resistance, sleeve friction, and pore pressures at different locations were recorded. Piezocone dissipation tests also were conducted at different penetration depths. High-quality Shelby tube samples were collected close to the PCPT tests and were used to carry out a comprehensive laboratory testing program. The (cv) values predicted by the different interpretation methods were compared with the reference values determined from the oedometer laboratory tests. The results of this study showed that two methods can estimate cv better than the other prediction methods.