US2372576A - Method of determining formation porosity during drilling - Google Patents

Method of determining formation porosity during drilling Download PDF

Info

Publication number
US2372576A
US2372576A US439636A US43963642A US2372576A US 2372576 A US2372576 A US 2372576A US 439636 A US439636 A US 439636A US 43963642 A US43963642 A US 43963642A US 2372576 A US2372576 A US 2372576A
Authority
US
United States
Prior art keywords
drilling
formation
porosity
pay
rate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US439636A
Inventor
John T Hayward
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to US439636A priority Critical patent/US2372576A/en
Application granted granted Critical
Publication of US2372576A publication Critical patent/US2372576A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B49/00Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
    • E21B49/003Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells by analysing drilling variables or conditions
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B44/00Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions

Definitions

  • This invention relates to a method for determining porosities of earth formations during drilling of wells by the rotary method, and particularly to a method for determining the porosity of oilor gas-containing formations during rotary drilling.
  • the final porosity determinations are, therefore, usually based on figures obtained from perhaps one percent or less of the total vertical section drilled, and such determinations are necessarily of questionable accuracy as applied to the entire section drilled.
  • the coring operation requires special tools and necessitates frequent interruptions in the normal drilling operations which are hazardous to the successful completion of the well, and in many cases, have caused a well to be lost.
  • This invention is based upon the discovery that because of the usually negligible porosity of the usual hard cap rock which normally overlies the relatively porous formation constituting the usual pay formation, the ratio of the drilling rate in the cap rock to that in the adjacent pay formation may be employed to determine the porosity of the pay formations.
  • the porosities of such porous formations may be determined directly from the drilling rates, during the course of conventional rotary drilling operations and without interruption of the normal drilling, and, of course, without recourse to core drilling heretofore employed to determine porosities.
  • the determination of the porosity of a pay formation may be, and usually is, made in a continuous manner for the entire vertical section of the formation as it is drilled, and the porosity value thus determined is found to be much more accurate for the entire section, than that obtained by the more conventional core analysis methods heretofore employed, which, as pointed out above, are necessarily based upon fragmentary portions of the drilled section.
  • the ratio of the drilling rate through a pay formation to the drilling rate through its cap rock is determined and this ratio, termed the drilling ratio is then co-related with a suitable porosity index which is constructed from such ratios which have been previously established for like formations in similar lithological sections.
  • a lithological section is intended to refer to that section of a well comprising a pay formation and its adjacent cap rock.
  • the porosity index referred to is preferably a curve showing the relationship of drilling ratios to porosity in a pay formation similar to that being examined and existing in a similar lithological section.
  • Such curves can be readily constructed on the basis of previous drilling rate and core analysis information which has been previously ascertained for areas where similar lithological sections exist, and such information is readily available to those engaged in the drilling industry.
  • Such curves may be prepared for the various types of pay formations, such as sands, limestones, and the like, for employment in accordance with this invention.
  • drilling is conducted in the usual manner by the rotary method to advance the drill through the cap rock formation and the immediately underlying pay formation. Precautions are normally taken to maintain substantially uniform drilling conditions during the advancement of the drill through both formations. Tnese drilling conditions include the rotational rate of the drill, the drilling fluid circulation rate, and the weight-on-bit.
  • the drilling rates through the cap rock and the pay formation are measured by any suitable or conventional means, and the ratio between them is determined, preferably by dividing the rate in the cap rock into the rate in the pay formation, in order that the resulting quotient, or drilling ratio, shall be a whole number, for purposes of convenience.
  • the drilling rate in the cap rock of a particular lithological section is 3 feet per hour, and in the immediately adjacent pay formation which is a sand, the drilling rate is 30 feet per hour.
  • the drilling ratio R will be found to be 10.
  • the values of the drilling ratios comprise the vertical axis and porosity (in percent) the horizontal axis.
  • a curve S is a porosity index characteristic of similar sand pay formation in similar lithological sections.
  • the value R is located as indicated, on the drilling ratio axis at the value 10. From this point a line is drawn horizontally to intersect the curve S and from this intersection, a line drawn vertically to the porosity axis will intersect the latter at the point P which gives the total porosity of the unknown pay formation as approximately 30.6 percent.
  • a curve L is also shown on the drawing to illustrate a, curve constituting a porosity index characteristic of a limestone pay formation and may be employed in a similar manner for determining the porosities of limestone pay formations.
  • the drilling rate may be continuously measured as the drill advances through the formation. Since the drilling rate through the cap rock will have already been determined the drilling ratio may be continuously determined as the drill proceeds through the pay formation, and the corresponding porosity can be determined from the chart. Obviously, if the pay formation is of relatively uniform hardness, the porosity of the entire pay formation will be substantially uniform. On the other hand, if the pay formation varies in hardness, the porosity of each vertical segment thereof may be determined by determining the drilling ratio for each segment as the drill advances, and co-relating these ratios with an applicable porosity index curve. In this way the true porosity value of the entire vertical section of the pay formation, or any segment thereof, may be obtained with much greater accuracy than has heretofore been possible.
  • the values of the changed conditions should be measured for each formation and correction factors supplied to the actual drilling rate measurements in order to correct these measurements for the changed conditions, so that the finally determined drilling rates shall be as though measured under uniform drilling conditions.
  • the effect of changes, particularly in rotational speed and weight-on-bit, on the drilling rates is now known, and suitable mathematical correction factors have been determined and may be readily applied where necessary.
  • the method of determining the porosity of an earth formation during the drilling of a well by the rotary system comprising progressively determining the rates of drilling at substantially uniform drilling progressively conditions, including rotational rate, drilling fluid circulation rate, and .weight-on-bit while drilling through a lithological section comprising a relatively hard formation and an adjacent relatively porous formation, whereby upon dividing the ascertained drilling rate for the relatively porous formation by the ascertained drilling rate for the relatively hard formation, there is established a drilling ratio which is characteristic of the porosity of said relatively porous formation, and co-relating said ratio with a porosity index for said relatively porous formation constructed from such drilling ratios previously established for a like formation in a similar lithological section.
  • the method of determining the porosity of an earth formation during the drilling of a well by the rotary system comprising, maintaining substantially uniform drilling conditions, including rotational rate, drilling fluid circulation rate and weight-on-bit, while drilling through a lithological section comprising a relatively hard formation and an adjacent relatively porous formation, measuring the rates of drilling through both said formations, whereby upon dividing the ascertained drilling rate for the relatively porous foramtion by the ascertained drilling rate for the relatively hard formation there is established a drilling ratio which is characteristic of the porosity of said relatively porous formation, and co-relating said ratio with a porosity index for said relatively porous formation constructed from such drilling ratios previously established for a like formation in a similar lithological section.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Earth Drilling (AREA)

Description

Raw;
METHOD OF DETERMINING FORMATION POROSITY DURING DRILLING D R A w Y A H J. 5 4 9 1 M H 2 :m M r m M 5 1 Filed April 20, 1942 INVENTOR JOHN T. HAYWARD ATTORNEY ssmuunttsmi Patented Mar. 27, 1945 UNITED STATES PATENT OFFICE METHOD OF DETERMINING FORMATION POROSITY DURING DRILLmG 2 Claims.
This invention relates to a method for determining porosities of earth formations during drilling of wells by the rotary method, and particularly to a method for determining the porosity of oilor gas-containing formations during rotary drilling.
The porosity of earth formations encountered in the drilling of oil and gas wells, and particularly the porosities of oiland gas-containing formations, has become a subject of increasingly great importance to the oil industry, since it is a prime factor in the estimation of petroleum reserves in place in oil and gas fields and in the determination of the probable productivity of such fields.
Heretofore the only method of determining the porosity of such a formation, which has been found acceptable, is that of core analysis, wherein a solid core sample of the formation, removed by one of the conventional core drilling methods,
is examined by physical methods to determine its porosity. This method has many disadvantages, due primari1y to the mechanical difliculty of cutting and removing from the well a continuous and unbroken section of the formation whose porosity is sought. Porous formations, particularly those containing oil or gas, are frequently loose, unconsolidated, sandy or shaly structures which undergo considerable crumbling and disintegration during the core drilling operation and under the washing action of the drilling fluid usually circulated during the drilling. As a result, core recoveries are seldom complete and from the core recovered only small selected pieces are normally tested for porosity. The final porosity determinations are, therefore, usually based on figures obtained from perhaps one percent or less of the total vertical section drilled, and such determinations are necessarily of questionable accuracy as applied to the entire section drilled. In addition, the coring operation requires special tools and necessitates frequent interruptions in the normal drilling operations which are hazardous to the successful completion of the well, and in many cases, have caused a well to be lost.
This invention is based upon the discovery that because of the usually negligible porosity of the usual hard cap rock which normally overlies the relatively porous formation constituting the usual pay formation, the ratio of the drilling rate in the cap rock to that in the adjacent pay formation may be employed to determine the porosity of the pay formations. As a result of this discovery, it is found that the porosities of such porous formations may be determined directly from the drilling rates, during the course of conventional rotary drilling operations and without interruption of the normal drilling, and, of course, without recourse to core drilling heretofore employed to determine porosities.
By the method in accordance with this invention, the determination of the porosity of a pay formation may be, and usually is, made in a continuous manner for the entire vertical section of the formation as it is drilled, and the porosity value thus determined is found to be much more accurate for the entire section, than that obtained by the more conventional core analysis methods heretofore employed, which, as pointed out above, are necessarily based upon fragmentary portions of the drilled section.
In accordance with this invention, the ratio of the drilling rate through a pay formation to the drilling rate through its cap rock is determined and this ratio, termed the drilling ratio is then co-related with a suitable porosity index which is constructed from such ratios which have been previously established for like formations in similar lithological sections.
For the purposes of this invention, a lithological section is intended to refer to that section of a well comprising a pay formation and its adjacent cap rock. The porosity index referred to is preferably a curve showing the relationship of drilling ratios to porosity in a pay formation similar to that being examined and existing in a similar lithological section. Such curves can be readily constructed on the basis of previous drilling rate and core analysis information which has been previously ascertained for areas where similar lithological sections exist, and such information is readily available to those engaged in the drilling industry. Such curves may be prepared for the various types of pay formations, such as sands, limestones, and the like, for employment in accordance with this invention.
The accompanying drawing illustrates a family of such curves.
In accordance with a general embodiment of this invention, drilling is conducted in the usual manner by the rotary method to advance the drill through the cap rock formation and the immediately underlying pay formation. Precautions are normally taken to maintain substantially uniform drilling conditions during the advancement of the drill through both formations. Tnese drilling conditions include the rotational rate of the drill, the drilling fluid circulation rate, and the weight-on-bit. The drilling rates through the cap rock and the pay formation are measured by any suitable or conventional means, and the ratio between them is determined, preferably by dividing the rate in the cap rock into the rate in the pay formation, in order that the resulting quotient, or drilling ratio, shall be a whole number, for purposes of convenience. By way of example, assume that the drilling rate in the cap rock of a particular lithological section is 3 feet per hour, and in the immediately adjacent pay formation which is a sand, the drilling rate is 30 feet per hour. The drilling ratio R. will be found to be 10. Referring to the chart shown in the drawing, the values of the drilling ratios comprise the vertical axis and porosity (in percent) the horizontal axis. A curve S is a porosity index characteristic of similar sand pay formation in similar lithological sections. The value R is located as indicated, on the drilling ratio axis at the value 10. From this point a line is drawn horizontally to intersect the curve S and from this intersection, a line drawn vertically to the porosity axis will intersect the latter at the point P which gives the total porosity of the unknown pay formation as approximately 30.6 percent.
A curve L is also shown on the drawing to illustrate a, curve constituting a porosity index characteristic of a limestone pay formation and may be employed in a similar manner for determining the porosities of limestone pay formations.
With the method of this invention, it is readily possible to continuously determine the porosity of the entire vertical section of the pay formation being drilled. Thus as the drill advances through the pay formation, the drilling rate may be continuously measured as the drill advances through the formation. Since the drilling rate through the cap rock will have already been determined the drilling ratio may be continuously determined as the drill proceeds through the pay formation, and the corresponding porosity can be determined from the chart. Obviously, if the pay formation is of relatively uniform hardness, the porosity of the entire pay formation will be substantially uniform. On the other hand, if the pay formation varies in hardness, the porosity of each vertical segment thereof may be determined by determining the drilling ratio for each segment as the drill advances, and co-relating these ratios with an applicable porosity index curve. In this way the true porosity value of the entire vertical section of the pay formation, or any segment thereof, may be obtained with much greater accuracy than has heretofore been possible.
As indicated above, it is important, in accordance with this invention, that the measurements of the drilling rates in the cap rock and pay formations be made under uniform drilling conditions of rotational speed, fluid circulation rate, and weight-on-bit. Accordingly, wherever possible or convenient, these conditions should normally be maintained uniform by the use of the usual drilling controls available for this purpose. In such cases, no measurement of these conditions need be made for purposes of correcting the drilling rates, since these factors will remain constant during the drilling of both formations. Frequently, however, practical considerations will require that some of these conditions, particularly the rotary speed or the weight-on-bit, should be changed from one formation to the other. Under these conditions, the values of the changed conditions should be measured for each formation and correction factors supplied to the actual drilling rate measurements in order to correct these measurements for the changed conditions, so that the finally determined drilling rates shall be as though measured under uniform drilling conditions. The effect of changes, particularly in rotational speed and weight-on-bit, on the drilling rates is now known, and suitable mathematical correction factors have been determined and may be readily applied where necessary.
It will be understood that other suitable mathematical functions of the drilling rates may be employed instead of the ratios of the drilling rates, for determining porosity of the formation, provided,- of course, a characteristic porosity index for co-relation purposes has first been established for similar pay formations in terms of those particular functions.
What I claim and desire to secure by Letters Patent is:
1. The method of determining the porosity of an earth formation during the drilling of a well by the rotary system, comprising progressively determining the rates of drilling at substantially uniform drilling progressively conditions, including rotational rate, drilling fluid circulation rate, and .weight-on-bit while drilling through a lithological section comprising a relatively hard formation and an adjacent relatively porous formation, whereby upon dividing the ascertained drilling rate for the relatively porous formation by the ascertained drilling rate for the relatively hard formation, there is established a drilling ratio which is characteristic of the porosity of said relatively porous formation, and co-relating said ratio with a porosity index for said relatively porous formation constructed from such drilling ratios previously established for a like formation in a similar lithological section.
2. The method of determining the porosity of an earth formation during the drilling of a well by the rotary system, comprising, maintaining substantially uniform drilling conditions, including rotational rate, drilling fluid circulation rate and weight-on-bit, while drilling through a lithological section comprising a relatively hard formation and an adjacent relatively porous formation, measuring the rates of drilling through both said formations, whereby upon dividing the ascertained drilling rate for the relatively porous foramtion by the ascertained drilling rate for the relatively hard formation there is established a drilling ratio which is characteristic of the porosity of said relatively porous formation, and co-relating said ratio with a porosity index for said relatively porous formation constructed from such drilling ratios previously established for a like formation in a similar lithological section.
JOHN T. HAYWARD.
US439636A 1942-04-20 1942-04-20 Method of determining formation porosity during drilling Expired - Lifetime US2372576A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US439636A US2372576A (en) 1942-04-20 1942-04-20 Method of determining formation porosity during drilling

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US439636A US2372576A (en) 1942-04-20 1942-04-20 Method of determining formation porosity during drilling

Publications (1)

Publication Number Publication Date
US2372576A true US2372576A (en) 1945-03-27

Family

ID=23745517

Family Applications (1)

Application Number Title Priority Date Filing Date
US439636A Expired - Lifetime US2372576A (en) 1942-04-20 1942-04-20 Method of determining formation porosity during drilling

Country Status (1)

Country Link
US (1) US2372576A (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2373053A1 (en) * 1976-11-11 1978-06-30 Texaco Development Corp METHOD AND APPARATUS FOR DETERMINING THE POROSITY OF FORMATIONS FROM INFORMATION OBTAINED DURING BORING
EP0163426A1 (en) * 1984-05-03 1985-12-04 Anadrill International SA Assessment of drilling conditions
US4627276A (en) * 1984-12-27 1986-12-09 Schlumberger Technology Corporation Method for measuring bit wear during drilling
US4852399A (en) * 1988-07-13 1989-08-01 Anadrill, Inc. Method for determining drilling conditions while drilling
EP0336491A1 (en) * 1988-04-04 1989-10-11 Anadrill International SA Method for detecting drilling events from measurement while drilling sensors
EP0351902A1 (en) * 1988-07-20 1990-01-24 Anadrill International SA Method of determining the porosity of an underground formation being drilled
US20220268152A1 (en) * 2021-02-22 2022-08-25 Saudi Arabian Oil Company Petro-physical property prediction

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2373053A1 (en) * 1976-11-11 1978-06-30 Texaco Development Corp METHOD AND APPARATUS FOR DETERMINING THE POROSITY OF FORMATIONS FROM INFORMATION OBTAINED DURING BORING
EP0163426A1 (en) * 1984-05-03 1985-12-04 Anadrill International SA Assessment of drilling conditions
US4627276A (en) * 1984-12-27 1986-12-09 Schlumberger Technology Corporation Method for measuring bit wear during drilling
EP0336491A1 (en) * 1988-04-04 1989-10-11 Anadrill International SA Method for detecting drilling events from measurement while drilling sensors
US4876886A (en) * 1988-04-04 1989-10-31 Anadrill, Inc. Method for detecting drilling events from measurement while drilling sensors
US4852399A (en) * 1988-07-13 1989-08-01 Anadrill, Inc. Method for determining drilling conditions while drilling
EP0350978A1 (en) * 1988-07-13 1990-01-17 Anadrill International SA Method for determining drilling conditions while drilling
EP0351902A1 (en) * 1988-07-20 1990-01-24 Anadrill International SA Method of determining the porosity of an underground formation being drilled
US4981036A (en) * 1988-07-20 1991-01-01 Anadrill, Inc. Method of determining the porosity of an underground formation being drilled
US20220268152A1 (en) * 2021-02-22 2022-08-25 Saudi Arabian Oil Company Petro-physical property prediction

Similar Documents

Publication Publication Date Title
CN108713089B (en) Estimating formation properties based on borehole fluid and drilling logs
US2214674A (en) Method of logging wells
US7532983B2 (en) Method and apparatus for measuring the wettability of geological formations
US4267726A (en) Well pressure testing method
JP2020527725A (en) Methods and systems for determining bulk density, porosity, and porosity distribution of surface formations
US2372576A (en) Method of determining formation porosity during drilling
CN106323835B (en) Method for determining cementing index of heterogeneous carbonate reservoir
Alger et al. New unified method of integrating core capillary pressure data with well logs
Thakur et al. The most common impacts of drilling dynamics and environments on log-while-drilling data: A study from Abu Dhabi
Avasthi et al. In-situ stress evaluation in the McElroy field, West Texas
US4052893A (en) Measuring reservoir oil saturation
Bragg et al. A comparison of several techniques for measuring residual oil saturation
Bilhartz Jr et al. Coring for in-situ Saturations in the Willard Unit CO2 Flood Mini-test
US2395617A (en) Method for determining the oil content of subterranean formations
Bianchi et al. Pressure Measurements Challenges in Low Permeability Reservoirs of Neuquén Basin, Argentina
US3670829A (en) Method for determining pressure conditions in a well bore from shale samples
Doerband Introducing a producible oil water contact (POWC) for better assessment of moveable oil in the transition zone
Forsyth et al. Investigating formation water salinity using a unique water extraction technique in a hydraulically active area
Proett et al. Real time pressure transient analysis methods applied to wireline formation test data
Liu et al. Challenges to geosteering and completion optimization of horizontal wells in the Cotton Valley Formation, East Texas
Mabile et al. An expert system helps in formation recognition
Noah Pore pressure evaluation from well logging and drilling exponent at Amal field, Gulf of Suez area, Egypt
Elmdahl The Fundamental Principles Of Core Analysis And Their Application To Gulf Coast Formations
CN118346267A (en) Formation pressure prediction method, device, equipment and medium based on resistivity while drilling
Parsons Caliper logging