The straight‐slope method for basement depth determination revisited

Geophysics ◽  
1993 ◽  
Vol 58 (4) ◽  
pp. 593-595 ◽  
Author(s):  
Jan Reidar Skilbrei
Keyword(s):  
Magnetic Anomaly ◽  
Inflection Point ◽  
Horizontal Projection ◽  
Slope Method ◽  
Source Estimation ◽  
Magnetic Source ◽  
Straight Line ◽  
Depth Determination ◽  
Basement Depth ◽  
General Reliability

The straight‐slope method is still popular for depth to magnetic source estimation due to its simplicity and general reliability in manual interpretation (e.g., Nettleton, 1976). Other commonly used manual slope methods are Peters rule (Peters, 1949) and Sokolov rule (Åm, 1972). The straight‐slope method uses the horizontal projection of the straightline part of the magnetic anomaly curve at the inflection point as the depth estimator (see Figure 1). Because no straight line exists mathematically, the rule is purely empirical, even though visually a certain part of a curve will appear to be straight.

On the half‐slope and straight‐slope methods of basement depth determination

Geophysics ◽  
1984 ◽  
Vol 49 (8) ◽  
pp. 1365-1368 ◽  
Author(s):  
D. Atchuta Rao ◽  
H. V. Ram Babu
Keyword(s):  
Horizontal Projection ◽  
The Past ◽  
Slope Method ◽  
Line Part ◽  
Straight Line ◽  
Depth Determination ◽  
Basement Depth ◽  
Prismatic Bodies ◽  
General Reliability ◽  
Exhaustive Study

Although a great variety of interpretation techniques for basement depth determination has been developed during the past two or three decades, the half‐slope and straight‐slope methods are still popular due to their simplicity and general reliability in manual interpretation and are widely used in oil exploration work (Nettleton, 1976). The half‐slope and straight‐slope rules are derived for a particular set of geologic/geophysical conditions and care should be taken in applying them in a more general way. For example, the half‐slope method of Peters (1949) was derived for magnetic anomalies over vertical dikes with vertical polarization. The straight‐slope method uses the horizontal projection of the straight‐line part of the steepest gradient at the inflection point on the anomaly curve as the depth estimator. This rule is purely empirical because mathematically there is no straightline part on the anomaly curve. Vacquier et al. (1951) made an exhaustive study of the straight‐slope method and presented several depth indices measured on different flanks of anomalies due to prismatic bodies.

On: “The straight‐slope method for basement depth determination revisited,” by J. R. Skilbrei (April 1993 GEOPHYSICS, 58, p. 593–595).

Geophysics ◽  
1994 ◽  
Vol 59 (5) ◽  
pp. 851-852
Author(s):  
Nelson C. Steenland
Keyword(s):  
Sedimentary Basins ◽  
Thin Plates ◽  
Aeromagnetic Data ◽  
Ancillary Data ◽  
Slope Method ◽  
Depth Determination ◽  
Basement Depth

After interpreting aeromagnetic data on a worldwide basis for more than 20 years without recourse to any ancillary data, subsequent basement drilling showed an accuracy of ±7.5 percent for the contoured maps, not individual depth values, of the bottom of new sedimentary basins. The fields were resolved into intrabasement, suprabasement, and intrasedimentary anomalies, and depths were computed to their sources of thick prisms and thin plates with two universally applied coefficients. More than once, intrasedimentary volcanics were handled routinely. The author’s statement in paragraph three of his Introduction is not correct.

Reply by the author to N. C. Steenland

Geophysics ◽  
1994 ◽  
Vol 59 (5) ◽  
pp. 852-852
Author(s):  
Jan R. Skilbrei
Keyword(s):  
Short Note ◽  
Volcanic Rocks ◽  
Sedimentary Basins ◽  
Slope Method ◽  
Depth Determination ◽  
Basement Depth ◽  
Limited Depth

Steenland writes that my statement in paragraph three of my Introduction is not correct. My statement is, “In most geological situations, and particular over sedimentary basins, the interpreter is unable to recognize bodies with limited depth extents.” It was implicit that I meant bodies within the basement with limited depth extents because the title of the short note is: “The straight‐slope method for basement depth determination revisited.” I believe that most interpreters agree with my statement. However, when it comes to recognizing intrasedimentary volcanics, I agree that it is often easy to distinguish these types of anomalies from those anomalies that are due to sources which exist within the basement when the volcanic rocks within the sediments are far removed above the basement.

scholarly journals Introduction and investigation of magnetic location system for steam-assisted gravity drainage dual-horizontal heavy oil wells

2018 ◽  
Vol 10 (9) ◽  
pp. 168781401879897 ◽  
Author(s):  
Yong Chen ◽  
Hao Yi ◽  
Chuan He
Keyword(s):  
Measurement Error ◽  
Oil Recovery ◽  
Detection System ◽  
Rapid Development ◽  
Gravity Drainage ◽  
Horizontal Projection ◽  
Recovery Method ◽  
Location System ◽  
Steam Assisted Gravity Drainage ◽  
Magnetic Source

Steam-assisted gravity drainage has been proven to be an effective oil recovery method, and the technology of magnetic location is the key to steam-assisted gravity drainage. In view of the rapid development of this technology in China, a new magnetic location system with intellectual property rights was developed in this article, including mechanical parts and circuit section of detection system. Specific structure, operating principle, and technical parameters of magnetic source generator and detection system were designed and analyzed. The ground test results show that the source generator is powered by an alternating current of 4–7 A, the detection system can probe the magnetic field signal 25 m away from the magnetic source generator, and the measurement error is less than 3% by comparison of measured with actual spacing distance. The steam-assisted gravity drainage dual-horizontal well group in Zhong 37 Well block in Fengcheng Oilfield is chosen for further experiment with the developed magnetic location technology. The results of field experiment show the trajectories of Wells I (injection well) and P (production well) are basically matched in the horizontal projection, and the measurement error is within the allowable range. The magnetic location system developed in this article can meet the operational requirement in steam-assisted gravity drainage dual-horizontal wells.

The programm for highlighting the main components resulting in the algebraic model of constructive logic

10.12737/5612 ◽  
2014 ◽  
Vol 8 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Хромушин ◽  
Viktor Khromushin ◽  
Хромушин ◽  
Oleg Khromushin
Keyword(s):  
Mathematical Model ◽  
Inflection Point ◽  
Detection Limits ◽  
Algebraic Model ◽  
Constructive Logic ◽  
Straight Line ◽  
Nonlinear Mathematical Models ◽  
Main Components ◽  
Combined Mark

The article presents the program to determine the principal components resulting in the algebraic model of constructive logic, which is designed for construction multivariate nonlinear mathematical models. The resulting mathematical model is represented by a set of resulting components as factors indicating the detection limits, combined mark of conjunction (indicating joint impact). Each resulting component is characterized by power, which is the essence of the number of rows in the table that match the specified detection limits factors in their joint action. The program provides two methods to determine the main result components. The first method is based on determining the minimum difference between increasing amounts of capacity resulting components of the top and bottom. The second method is based on the determination of the inflection point of the curve decreasing capacity of the resulting components. The authors give recommendations on the choice of allocation method the main result components. If the curve changes power has a dedicated point of inflection and more like a straight line, it is recommended to use method 1. If the curve changes power has a dedicated point of inflection, it is recommended to use method 2. The program should be used in the package of analytical programs algebraic model of constructive logic when performing complex analytical calculations in biophysics, medicine and biology.

scholarly journals ANALYSIS OF HIGH RESOLUTION AEROMAGNETIC DATA OF SOME PARTS OF BENUE TROUGH, NIGERIA

2020 ◽  
Vol 4 (2) ◽  
pp. 76-85
Author(s):  
Nuraddeen Usman ◽  
Ibrahim Jibril
Keyword(s):  
Spectral Analysis ◽  
Magnetic Anomalies ◽  
Aeromagnetic Data ◽  
Benue Trough ◽  
First Order ◽  
Qualitative Interpretation ◽  
Maximum Value ◽  
Magnetic Source ◽  
Analysis Technique ◽  
Basement Depth

This work is aimed to determine the depth to basement of some magnetic sources in the study area. Four aeromagnetic sheets were acquired from the Nigerian Geological Survey Agency which includes (Bajoga, 131, Gulani, 132, Gombe, 152 and Wuyo, 153). The study area covers an estimated area of about 12100km2 between latitude 90N-110N and longitude 110E-130E. The total magnetic field of the study area have been evaluated. In order to determine the basement depth, spectral analysis technique was applied. Detailed analysis of the aeromagnetic data for the study area was performed. The procedure involved in the analysis include reduction to equator to remove the effect of inclination, contouring of the total magnetic intensity, separation of the regional and residual anomalies using polynomial fitting of first order, qualitative interpretation and quantitative interpretation. The residual field of the study area composes of low magnetic anomalies reaching a minimum value of -158.6nT as observed in the northern and southern parts and high magnetic anomalies reaching a maximum value of 178.1nT as observed in the western part of the study area. The result from the spectral analysis for each block shows that the depths to the magnetic source are 5.20Km for block 1, 5.74Km for block 2, 7.59Km for block 3 and 3.56Km for block 4. The average depth to magnetic source in the study area was found to be 5.52Km. Based on the computed average sedimentary thickness obtained in this study area, hydrocarbon accumulation in the study area is feasible.

scholarly journals Source Depth Determination from Aeromagnetic Data of Ilesha, Southwest Nigeria, Using the Peters’ Half Slope Method

2013 ◽  
Vol 3 (1) ◽  
Author(s):  
Vitalis Chidi Ozebo ◽  
Charles Olubunmi Ogunkoya ◽  
Victor Makinde ◽  
Gideon O. Layade
Keyword(s):  
Aeromagnetic Data ◽  
Source Depth ◽  
Slope Method ◽  
Depth Determination ◽  
Southwest Nigeria
Sign in / Sign up

Export Citation Format

Share Document