Training in the earth's Physically Deterministic
Force Balance

Courses , Seminars and Mentoring in Earth Mechanics for geologists and upstream subsurface engineering are available. Subsurface mechanical problems are most easily solved through understanding the earth's governing physics.

Near mudline soil mechanics including compaction are related to sediment acoustic properties through the Extended Elastic Equations of Hooke's law.

Deterministic Earth Mechanical Science for Subsurface
Geoscientists and Engineers
by Phil Holbrook Ph.D.

Drilling safety, efficiency and the production of hydrocarbons depend on subsurface mechanics. The stresses and fluid pressures in the earth can be predicted deterministically. Earth mechanical science is a unification of accepted physical-mathematical laws that act through the in situ earth matter. These predictive laws can be readily understood by subsurface geoscientists and engineers.

Natural minerals and fluids are the minimum energy forms of matter that compose almost all of the earth. Minerals and fluids either rest or move toward lower energy positions under the direct influence of physical laws. Physical first principles and conservation laws apply below the earth’s surface as well as above.

Hydrocarbon move with water until their capillary pressure is less than the pore throat or fracture entry pressure. Fracture permeability is highly stress dependant while inter-granular permeability is lithology and porosity dependant. Hydrocarbon traps are local fluid energy minima. They can be detected through reflection seismic means and mechanically verified before the risk and expense of drilling.

Blowouts, well-bore collapse, and lower hydrocarbon production are unwanted consequences of poor mechanical understanding. Deterministic earth mechanical science provides physical understanding for good decision making.

Deterministic earth mechanical science has the fewest possible fitting coefficients. Mass, energy, and depth linkages are dimensionally correct. All subsurface stresses and pressures depend upon the tectonic regime, porosity, mineral and fluid properties. Most of these are known a priori and can be verified in whole or part through independent measurements.

There are three discrete energy minima that correspond with the earths three tectonic regimes. They occur along 1.) leading, 2.) sheared, or 3.) trailing plate margins. [Mass-energy] and [stress/strain] are both conserved in three mechanically compatible closed forms. Their combined deterministic explanations are globally applicable for planet earth.    RETURN TO TOP

Who should take this course?

Anyone with decision making authority in well planning, drilling, or reservoir production. Well bore diameter and casing point selection are co-dependant variables for every drilling prospect. The elimination of un-necessary casing strings by judicious choices of casing seat depths can save millions of dollars in drilling costs. These decisions depend on lithology, fluid pressure and stress. Small changes in casing seat selections can result in significant changes in drilling costs.  RETURN TO TOP

Course Description and Outline

TPrior art methods involve only slight variations of (empirical depth function) forced fitting. Tweaking empirical energy-depth functions is dimensionally and conceptually incorrect. It is a never ending, subjective, and uncertain process. Some of the theory of deterministic earth mechanical science must be taught whatever the practical application.

Well planners, drillers and reservoir engineers have different needs that could shorten or lengthen some parts of a comprehensive course. The outline below is a full course menu from which some might choose to learn some things and not others. These audience accommodations can be made either before or during the course.

Two books contain the whole theory. "Deterministic Earth Mechanical Science" emphasizes underlying molecular mechanical and energy minimization theory. The contributors to the composite theory are duly noted. "Pore pressure through Earth Mechanical Systems" emphasizes macro-physical relationships that can be correlated directly to measurements. Many subsurface trends are shown in both books as well. The physical theory book draws upon but does not duplicate the macro-physical book.

The chapter outlines and list of figures of both books are available. They are Web-broc.pdf for "Deterministic Earth Mechanical Science" and cover_itx.doc. for "Pore pressure through Earth Mechanical Systems" . These books are a guide for a comprehensive earth mechanical course. Some audiences may be interested in only a few subject areas.

Other related courses on borehole wall mechanics, drilling mechanics, elastic acoustic rock responses, and petrophysical relationships can also be taught. These are all mechanically inter-dependant but are not fully covered in the two published books.

Short courses from 2 hours to 4 days are available depending on the level of detail that is wanted. Introductory seminars that cover the both theory and application in about one hour can also be presented.

The sample short course described below is a one-day course that was taught to rock mechanics professionals. Other courses directed toward Geophysicists, Drilling Engineers and Pore pressure professionals . Each technical specialty depends on earth mechanics which can be calculated and predicted deterministically!   RETURN TO TOP

Pore pressure through Earth Mechanical Systems

The North American Rock Mechanics Association Short Course
presented at DCROCKS July 7, 2001 Washington, DC

Minerals and fluids are the earth’s molecular scale building blocks. All loads, effective stresses and pressures are generated by and transmitted through minerals and fluids. "Pore pressure through Earth Mechanical Systems", explains earth mechanics as constitutive pressure-stress/strain relationships.

Mineral ionic bonds can support stress anisotropy. Fluid compressibility is volumetric and isotropic. The earth subsurface environment is now understood through physically representative, closed-form mathematical formulations. These incorporate the governing physical laws. Earth mechanical systems are force balanced, and dimensionally correct in closed mathematical forms. Earth in situ mechanical systems are quantitatively related to the mineral and fluid substances of the earth. 

Pore pressure through Earth Mechanical Systems is recommended for geologist and engineers that are involved in sub-surface drilling or engineering. Earth mechanical systems relate rock properties directly to their in situ load environment. The mechanical interactions between pore fluid pressure (P_P), fracture propagation pressure (P_F), overburden (S_v), average mineralogy, and porosity of sedimentary rocks are explained through recently formulated earth mechanical systems.   RETURN TO TOP

COURSE OUTLINE 1.) The controlling physics: Newtonian gravitation is balanced against absolute in situ strain under Effective Stress Theorem boundary conditions. Stress/strain hysteresis in granular solids is related to end-member mechanical systems. Borehole in situ leakoff tests are directly related to their far field stress limits. 2.) The primary controls of grain-matrix compaction are mineral grain hardness and clay mineral inter-particle repulsive force. 3.) Claystone end-member and non-clay mineral compaction curves are demonstrated to be power-law in situ effective stress/strain functions.

4.) Minimum horizontal effective stress is directly related to in situ strain in Normal Fault Regime » biaxial basins. Stress ratios in strike-slip tectonic regimes also tend strongly toward even number proportionality. 5.) Mineralogically sensitive porosity transforms for g-g density; resistivity and full-waveform sonic sensors are explained.

6.) Overburden, Pore pressure and Fracture propagation pressure are mathematically defined as loads within the earth grain-matrix-compactional mechanical system. This mechanical system of equations uses only material property coefficients of minerals and fluids that compose the earth.

Some indirect earth mechanical system inter-relationships are; 7.) Pore pressure within continuous permeable "pressure compartments" is regulated by the minimum work fracture pressure. 8.) HPHT fluid expansion pore pressure is measurable using a regionally calibrated un-loading limb effective stress/strain relationship. The calibration procedure and its mechanical significance are related and described.

Empirical "Normal compaction vs. depth trend" pore pressure methods have existed for 35 years. The important aspects of these 250+ non-physical empirical methods and their operator forced intersections with earth’s mechanical systems are explained.

Following this course, the student should have a fundamental understanding of a.) The sensor specific transforms that are used to estimate porosity and mineralogy; b.) The grain-matrix loading and un-loading limb effective stress/strain relationships and c.) Earth pore pressure « effective stress interactions that regulate pore pressure profiles in the subsurface. These earth mechanical system inter-dependencies relate the loads, effective stresses, pore pressure to physical properties at the borehole wall. Many drilling and reservoir engineering applications depend on all this borehole wall information.   RETURN TO TOP

COURSE SCHEDULE Pore pressure through Earth Mechanical Systems

8:30 – 9:00 The controlling physics; Newtonian gravitation is balanced by absolute in situ strain under Effective Stress Theorem boundary conditions. Stress/strain hysteresis in granular solids is related to end-member mechanical systems. The relationships of borehole leakoff tests to the limiting far-field stresses is explained and demonstrated.

9:00 - 9:30 The primary controls of grain-matrix compaction are intra-mineral-grain hardness and clay mineral inter-particle repulsive force. Both are power-law relationships.

9:30 - 10.00 Claystone end-member and non-clay mineral compaction vs. depth curves are demonstrated to be mechanically representative power-law linear in situ effective stress/strain functions.

10:00 – 10:30 Break & Informal Q&A.

10:30 – 11:00 h/v stress ratio; Stress is transmitted across a given fault block through the rock grain matrix. Within each Andersonian fault regime block, there are apparently fixed stress/stress and stress/strain ratios. Minimum horizontal/vertical effective stress is directly related to in situ strain in Normal Fault Regime » biaxial basins. A simple mathematical H>v>h effective stress ratio/strain relationship is also apparent in Strike-Slip basins.

11:00 – 12:00 Mineral and fluid sensitive porosity transforms for g-g density, resistivity and full-waveform sonic sensors are physical properties inter-related and explained.

12:00 – 1:30 Lunch with open discussions;

1:30 – 2:00 Closed-form grain-matrix-compactional mechanical systems: Pore pressure and Fracture propagation pressure are mathematically defined as inter-dependant loads within the earth grain-matrix-compactional mechanical system. The relationship between the elastic, and grain-matrix-compactional, mechanical system domains are explained.

2:00 – 2:30 Indirect earth mechanical system inter-relationships: Pore pressure within continuous permeable "pressure compartments" is regulated by the minimum work fracture pressure of that compartment. The nature of this mechanical system is explained.

2:30 – 3:00 HPHT fluid expansion pore pressure is measured using a regionally calibrated un-loading limb effective stress/strain relationship. The calibration procedure and its mechanical loading vs. un-loading significance are related, explained and described.

3:00 – 3:30 Break & Informal Q&A.

3:30 – 4:00 Earth Mechanical Systems vs. Porosity Relationships: All the elastic (Hooke’s law), grain-matrix-compactional, and un-loading effective stress/strain functions are mathematically and compositionally related power-law linear earth’s mechanical systems.

4:00 – 4:30 Empirical "Normal compaction vs. depth trend" pore pressure methods have existed for 35 years. There are 250+ non-physical methods. Empirical pore pressure methods are tangential approximations to earth mechanical systems. Apparent success occurs when the operator forces non-physical intersections with the earth’s mechanical systems. Empirical curve fit methods do not use mechanical boundary condition. Strain is not used. Stresses and strain are not balanced and units do not cancel.

4:30 – 5:00 Earth Mechanical Systems Summary; The earth has several mechanical systems that relate stress/strain to mineralogy and porosity. Hooke’s law and the grain-matrix-compactional mechanical system are analogous and related to each other. The Effective Stress Theorem boundary condition is fundamentally related to volumetric in situ strain in closed mathematical form.

5:00 Adjourn

Following this course, each student should have a fundamental understanding of a.) The sensor specific transforms that are used to estimate porosity and mineralogy; b.) The grain-matrix loading and un-loading limb effective stress/strain relationships and c.) Earth pore pressure « effective stress interactions that regulate pore pressure profiles in the subsurface. These earth mechanical system inter-dependencies directly relate the loads, effective stresses, pore pressure and physical properties at the borehole wall. Many drilling and reservoir engineering applications depend on this information.   RETURN TO TOP

BIOGRAPHY OF LECTURER

Phil Holbrook received his Ph.D. in Geology from Penn State in 1973. He entered Gulf Oil Company’s one year Experience Broadening program in Exploration Geophysics. In exploration operations, he interpreted seismic data, developed drilling prospects, and supervised acquisition of geophysical data and well logging. He subsequently coordinated Gulf’s EB program and performed research on petrophysical oil exploration applications. He worked at Exxon Production Research for 8 years doing reservoir studies, seismic well ties, borehole televiewer operations, and served as an internal well log analyst - petrophysicist consultant to Exxon’s operations divisions.

He joined Sperry-Sun and began work on the only mechanically representative pore pressure and fracture pressure prediction methodology in 1985. This physically representative methodology has been applied to over 300 wells worldwide. He has studied earth mechanics, written two books and over 25 technical papers. Presently he consults on petrophysics, earth in situ and borehole relative force balance and rock mechanics. He performs applications research projects; and teaches on these subjects that are important to earth science. The earth mechanical system limits most oilfield mechanical operations such as drilling, setting casing, completion and reservoir mechanics.

For Courses, Seminars and/or Mentoring information you can contact Phil Holbrook by e-mail  phil@force-balanced.net for details.    RETURN TO TOP