Objective Evaluation of Preconsolidation Stress for Soft Clays from Constant Rate of Strain Pore Pressure Data

2007 ◽  
Author(s):  
Don J. DeGroot ◽  
Melissa M. Landon ◽  
Robert M. Ryan
Keyword(s):  
Pore Pressure ◽  
Objective Evaluation ◽  
Pressure Data ◽  
Soft Clays ◽  
Constant Rate

Charactervation of Adhesion in Thin-Film Materials by the Blister Test

1992 ◽  
Vol 276 ◽  
Author(s):  
Y Z. Chu ◽  
H. S. Jeong ◽  
R. C. White ◽  
C. J. Durning
Keyword(s):  
Fluid Pressure ◽  
Structural Features ◽  
Adhesion Energy ◽  
Pressure Data ◽  
Blister Test ◽  
Constant Rate ◽  
Polymer Metal ◽  
Metal Interfaces ◽  
Peel Tests ◽  
Microscopic Dynamic

ABSTRACTIn this work a blister test is applied to study the adhesion of thin films to substrates. In the blister test one injects a fluid at constant rate at the interface between the substrate and an overlayer to create a “blister”. The fluid pressure is measured as function of time. An analysis gives a reliable way of calculating the adhesion energy Ga. from the time-dependent pressure data. The method was applied to a variety of systems including polymer/polymer, polymer/silicon and polymer/metal interfaces. The results show that the test is very sensitive and is able to determine small adhesion energies inaccessible in conventional peel tests. This work demonstrates that the blister test provides a means of relating the mechanical strength of an interface to its microscopic dynamic and structural features.

Weighted residual approach to constant strain rate test

2011 ◽  
Vol 48 (4) ◽  
pp. 671-675 ◽  
Author(s):  
Dieter Stolle ◽  
Jonathan Stolle
Keyword(s):  
Strain Rate ◽  
Pore Pressure ◽  
Constant Strain Rate ◽  
Time Factors ◽  
Transient Effects ◽  
Coefficient Of Consolidation ◽  
Virtual Displacement ◽  
Constant Rate ◽  
Rate Test ◽  
Displacement Approach

This note presents a virtual displacement approach to analyze the constant rate of strain consolidation test. It yields simplified “exact” equations within the weighted residual context for interpreting test data. Equations corresponding to larger time factors are similar to those presented in the literature, although the transient effects are clearer than in previous formulations. An advantage of the framework is that assumptions concerning the uniformity of properties through a sample can be relaxed. The derivation shows that E must be constant for the coefficient of consolidation to be independent of position. Depending on the sequencing of sublayers, it is shown that basal pore pressure can be higher or lower for layered media compared with uniform material when allowing E to vary, even though cv is kept constant.

Practical Application of Pressure-Rate Deconvolution to Analysis of Real Well Tests

2005 ◽  
Vol 8 (02) ◽  
pp. 113-121 ◽  
Author(s):  
Michael M. Levitan
Keyword(s):  
Test Data ◽  
Rate Data ◽  
Well Test ◽  
Pressure Data ◽  
Well Test Analysis ◽  
Test Analysis ◽  
Deconvolution Algorithm ◽  
Constant Rate ◽  
Test Pressure ◽  
Real Test

Summary Pressure/rate deconvolution is a long-standing problem of well-test analysis that has been the subject of research by a number of authors. A variety of different deconvolution algorithms have been proposed in the literature. However, none of them is robust enough to be implemented in the commercial well-test-analysis software used most widely in the industry. Recently, vonSchroeter et al.1,2 published a deconvolution algorithm that has been shown to work even when a reasonable level of noise is present in the test pressure and rate data. In our independent evaluation of the algorithm, we have found that it works well on consistent sets of pressure and rate data. It fails, however, when used with inconsistent data. Some degree of inconsistency is normally present in real test data. In this paper, we describe the enhancements of the deconvolution algorithm that allow it to be used reliably with real test data. We demonstrate the application of pressure/rate deconvolution analysis to several real test examples. Introduction The well bottomhole-pressure behavior in response to a constant-rate flow test is a characteristic response function of the reservoir/well system. The constant-rate pressure-transient response depends on such reservoir and well properties as permeability, large-scale reservoir heterogeneities, and well damage (skin factor). It also depends on the reservoir flow geometry defined by the geometry of well completion and by reservoir boundaries. Hence, these reservoir and well characteristics are reflected in the system's constant-rate drawdown pressure-transient response, and some of these reservoir and well characteristics may potentially be recovered from the response function by conventional methods of well-test analysis. Direct measurement of constant-rate transient-pressure response does not normally yield good-quality data because of our inability to accurately control rates and because the well pressure is very sensitive to rate variations. For this reason, typical well tests are not single-rate, but variable-rate, tests. A well-test sequence normally includes several flow periods. During one or more of these flow periods, the well is shut in. Often, only the pressure data acquired during shut-in periods have the quality required for pressure-transient analysis. The pressure behavior during the individual flow period of a multirate test sequence depends on the flow history before this flow period. Hence, it is not the same as a constant-rate system-response function. The well-test-analysis theory that evolved over the past 50 years has been built around the idea of applying a special time transform to the test pressure data so that the pressure behavior during individual flow periods would be similar in some way to constant-rate drawdown-pressure behavior. The superposition-time transform commonly used for this purpose does not completely remove all effects of previous rate variation. There are sometimes residual superposition effects left, and this often complicates test analysis. An alternative approach is to convert the pressure data acquired during a variable-rate test to equivalent pressure data that would have been obtained if the well flowed at constant rate for the duration of the whole test. This is the pressure/rate deconvolution problem. Pressure/rate deconvolution has been a subject of research by a number of authors over the past 40 years. Pressure/rate deconvolution reduces to the solution of an integral equation. The kernel and the right side of the equation are given by the rate and the pressure data acquired during a test. This problem is ill conditioned, meaning that small changes in input (test pressure and rates) lead to large changes in output result—a deconvolved constant-rate pressure response. The ill-conditioned nature of the pressure/rate deconvolution problem, combined with errors always present in the test rate and pressure data, makes the problem highly unstable. A variety of different deconvolution algorithms have been proposed in the literature.3–8 However, none of them is robust enough to be implemented in the commercial well-test-analysis software used most widely in the industry. Recently, von Schroeter et al.1,2 published a deconvolution algorithm that has been shown to work when a reasonable level of noise is present in test pressure and rate data. In our independent implementation and evaluation of the algorithm, we have found that it works well on consistent sets of pressure and rate data. It fails, however, when used with inconsistent data. Examples of such inconsistencies include wellbore storage or skin factor changing during a well-test sequence. Some degree of inconsistency is almost always present in real test data. Therefore, the deconvolution algorithm in the form described in the references cited cannot work reliably with real test data. In this paper, we describe the enhancements of the deconvolution algorithm that allow it to be used reliably with real test data. We demonstrate application of the pressure/rate deconvolution analysis to several real test examples.

scholarly journals Pore Pressure Prediction Using Artificial Neural Network Based On Logging Data

2020 ◽  
Vol 4 (1) ◽  
pp. 33
Author(s):  
RAKA SUDIRA WARDANA ◽  
Meredita Susanty ◽  
Hapsoro B.W
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Pore Pressure ◽  
Direct Measurement ◽  
Empirical Models ◽  
Measurement Methods ◽  
Pressure Data ◽  
Pore Pressure Prediction ◽  
Drilling Operations ◽  
Artificial Neural

Pore pressure is a critical parameter in designing drilling operations. Inaccurate pore pressure data can cause problems, even incidents in drilling operations. Pore pressure data can be obtained from direct measurement methods or estimated using indirect measurement methods such as empirical models. In the oil and gas industry, most of the time, direct measurement is only taken in certain depth due to relatively high costs. Hence, empirical models are commonly used to fill in the gap. However, most of the empirical models highly depend on specific basins or types of formation. Furthermore, to predict pore pressure using empirical models accurately requires a good understanding in determining Normal Compaction Trendline. This proposed approach aims to find a more straightforward yet accurate method to predict pore pressure. Using Artificial Neural Network Model as an alternative method for pore pressure prediction based on logging data such as gamma-ray, density, and sonic log, the result shows a promising accuracy.

scholarly journals Pre-drill pore pressure prediction and safe well design on the top of Tulamura anticline, Tripura, India: a comparative study

2019 ◽  
Vol 10 (3) ◽  
pp. 1021-1049
Author(s):  
Mohatsim Mahetaji ◽  
Jwngsar Brahma ◽  
Anirbid Sircar
Keyword(s):  
Pore Pressure ◽  
Seismic Data ◽  
New Method ◽  
Burst Pressure ◽  
Velocity Data ◽  
Pressure Data ◽  
Collapse Pressure ◽  
Fracture Pressure ◽  
Well Design ◽  
Pore Pressure Prediction

AbstractThe Tulamura anticline falls in the state Tripura, Northeast India. The anticline is extended up to neighbour country Bangladesh. The region is characterized by huge anticlines, normal faults and abnormally pressured formations which causes a wide margin of uncertainties in wildcat well planning and design. These geological complexities of Tulamura anticline make the drilling engineers more challenging. Therefore, a proper well design is essential in such a region to prevent blowout. Drilling engineer requires to maintain wellbore pressure between the pore pressure and fracture pressure to reduce the possibility of a kick and a formation damage. Pore pressure plays an important role to design a safe and economical well in such a high pressure and temperature reservoir. For wildcat drilling, only seismic data are available in the study area. There are various methods to predict pore pressure from seismic velocity data. Modified Eaton’s method is widely used for the pore pressure prediction from seismic data in terms of the velocity ratio. Modified Eaton’s equations may cause an error by manual selection of compaction trend line which is used to find normal compaction velocity. The main objectives of this study are to develop a new method to predict pore pressure and safe well design on the top of Tulamura anticline in terms of pore pressure. The new method is validated by a well-known method, modified Eaton’s method, and RFT pressure data from offset wells. An excellent match with pore pressures estimated from RFT pressure data and predicted by new model along with modified Eaton’s method is observed in this research work. The efficiency and accuracy level of the hybrid model is more as compared to other methods as it does not require compaction velocity data; thus, an error caused by manual compaction trend can be eliminated. Pore pressure predicted by new method indicates result up to the 6000 m, which is up to the basement rock. The predicted pore pressures by new method are used as an input to calculate the fracture pressure by Hubbert and Willis method, Mathews and Killy method and modified Eaton’s method. Equivalent mud weight selection is carried out using median line principle with additional 0.3 ppg, 0.3 ppg and 0.2 ppg of swab pressure, surge pressure and safety factor, respectively, for calculation of all casing pipes. Casing setting depths are selected based on pore pressure gradient, fracture pressure gradient and mud weight using graphical method. Here, four types of casing setting depths are selected: conductor, surface, intermediate and production casings at 100 ft, 6050 ft, 15500 ft and 18,500 ft, respectively, by new methods, but the casing setting depths for intermediate are at 13500 ft in the case of modified Eaton’s method. The casing policy is selected based on burst pressure, collapse pressure and tension load. For each casing, kick tolerance in bbl is determined from kick tolerance graph to prevent the blowout. Finally, comparative safe and economical wells are designed on the top of Tulamura anticline along with target depth selection, casing setting depth selection, casing policy selection and kick tolerance in consideration of collapse pressure, burst pressure and tension load which gives a clear picture of well planning on the top of anticline in pore pressure point of view.

An approach for the determination of the preconsolidation pressure in sensitive clays

1980 ◽  
Vol 17 (3) ◽  
pp. 446-453 ◽  
Author(s):  
S. Leroueil ◽  
J. P. LeBihan ◽  
F. Tavenas
Keyword(s):  
Pore Pressure ◽  
Theoretical Basis ◽  
Axial Stress ◽  
New Method ◽  
One Stage ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Constant Gradient ◽  
Oedometer Tests

The present methods for the determination of the preconsolidation pressure of clays are time consuming and expensive. A new method is proposed in which the clay is loaded in a "one-stage loading" to an axial stress in excess of the estimated preconsolidation pressure. The preconsolidation pressure is determined from the observation of the pore pressure dissipation within a few hours. The theoretical basis of this method is also used to discuss the method of interpreting constant rate of strain and constant gradient oedometer tests.

Monotonic and dilatory pore-pressure decay during piezocone tests in clay

1998 ◽  
Vol 35 (6) ◽  
pp. 1063-1073 ◽  
Author(s):  
S E Burns ◽  
P W Mayne
Keyword(s):  
Pore Pressure ◽  
Pore Water Pressure ◽  
Soil Mechanics ◽  
Water Pressure ◽  
Cavity Expansion ◽  
Coefficient Of Consolidation ◽  
Soft Clays ◽  
Fine Grained ◽  
Cavity Expansion Theory ◽  
Pore Pressure Response

During a pause in cone penetration in fine-grained soils, pore-water pressure dissipation tests are performed to evaluate the coefficient of consolidation. For standard piezocones with shoulder filter elements, soft clays and silts show a monotonically decreasing response with time; however, dissipation tests performed in heavily overconsolidated silts and clays show dilatory behavior, with the pore-pressure behavior increasing from the initial measured value to a maximum, and then decreasing to hydrostatic values. This paper presents a theoretical framework which combines cavity-expansion theory and critical-state soil mechanics with an analytical solution to the radial consolidation equation. The method is able to describe the pore-pressure response curve for dissipation tests performed in soils which demonstrate either monotonically decreasing or dilatory pore-pressure behavior.Key words: cavity expansion, consolidation, piezocone, pore pressure.

New method to determine proper strain rate for constant rate-of-strain consolidation tests

2012 ◽  
Vol 49 (1) ◽  
pp. 18-26 ◽  
Author(s):  
A. Tolga Ozer ◽  
Evert C. Lawton ◽  
Steven F. Bartlett
Keyword(s):  
Strain Rate ◽  
Linear Equation ◽  
Pore Pressure ◽  
Void Ratio ◽  
Semiempirical Method ◽  
The Other ◽  
Initial Void Ratio ◽  
Constant Rate ◽  
Loading Tests ◽  
Incremental Loading

The development of a new semiempirical method to predict the proper strain rate for constant rate-of-strain (CRS) consolidation tests is described herein. The validity of the proposed method is analyzed using experimental results from CRS and incremental loading tests on four types of soil: Lake Bonneville clay, Massena clay, kaolinite, and montmorillonite. It is found that the maximum allowable strain rate depends on the initial void ratio of the soil and thus is related to the compressibility of the soil. The effect of the strain rate on the distribution of the pore pressure within the sample is investigated by comparing values of effective vertical stress calculated using a linear equation published by Wissa et al. in 1971 with values of effective stress at the base of the specimen determined from measured values of pore pressure. Overall, the proposed method predicts the maximum allowable strain rate very well for three of the four soils and moderately well for the other soil.

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