Method and apparatus for producing a new output record medium illustrating a quantitative description in the volume dimension of mud filtrate invasion into permeable zones of a formation in a wellbore

• US 5,379,216 A
• Filed: 05/27/1992
• Issued: 01/03/1995
• Est. Priority Date: 05/27/1992
• Status: Expired due to Term

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Head, Elton L.
• Primary Examiner(s): Hayes, Gail O.
• Assistant Examiner(s): BODENDORF, ANDREW
• Application Number:
  US07/889,545
• Time in Patent Office: 951 Days
• Field of Search: 364/422, 73/152, 73/153
• US Class Current: 702/12
• CPC Class Codes: E21B 47/113 using electrical indications; using light radiations
• CPC Class Codes: E21B 49/00 Testing 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
• CPC Class Codes: G01V 3/38 Processing data, e.g. for analysis, for interpretation, for correction

Abstract

A volume transform system, which includes a computer processor and a novel volume transform software, receives a set of invasion parameters from a parameterization system, the parameterization system producing a set of invasion parameters which represent a resistivity profile of a formation traversed by a wellbore. The volume transform system functions to perform a quantitative invasion analysis on the invasion parameters in the volume dimension by computing the volume of mud filtrate (Vmf) for each unit of depth in the wellbore and producing a new output record medium, or a new log, which quantitatively illustrates the volume of the mud filtrate (vmf) invasion into the formation traversed by the wellbore as a function of depth in the wellbore. The aforementioned quantitative invasion analysis in the volume dimension compensates for variations in drilling mud, porosity, formation water, and saturation gradient from well to well and between hydrocarbon and water zones with a wellbore.

Claims

1. A system responsive to a set of invasion parameters associated with each unit of depth in a wellbore for generating an output record medium, comprising:

first means responsive to the set of invasion parameters associated with said each unit of depth in said wellbore for determining a corresponding volume of mud filtrate which has invaded into permeable zones of a formation traversed by said wellbore for a given thickness at said each unit of depth in said wellbore,

said permeable zones of formation at said each depth in said wellbore including a flushed zone, an uninvaded zone, and a transition zone interposed between said flushed zone and said uninvaded zoned,

said invasion parameters including a resistivity of the flushed zone (Rxo), a radius (r₁) measured from a wall of said wellbore to an outer radial extremity of said flushed zone, and a radius (r₂) measured from a wall of said wellbore to an inner radial extremity of said uninvaded zone,

said first means determining said volume of mud filtrate invasion into said flushed zone and said transition zone of said formation for a given thickness at said each unit of depth in said wellbore by using the following equation;

space="preserve" listing-type="equation">Vmf=3.1416 . . . /3[(Rmf/Rxo).sup.1/n ][r.sub.1.sup.2 +(r.sub.1)(r.sub.2)+r.sub.2.sup.2 -3r.sub.b.sup.2 ],

where Vmf is the volume of mud filtrate, Rmf is the resistivity of said mud filtrate, and r_b is the radius of said wellbore; and

output record generating means responsive to the volume of mud filtrate invasion into said permeable zones of said formation for said given thickness at said each unit of depth in said wellbore determined by said first means for generating an output record medium illustrating said volume of mud filtrate invasion into said permeable zones of said formation at said each unit of depth in the wellbore.

2. The system of claim 1, wherein said output record generating means generates said output record medium, said output record medium illustrating said volume of mud filtrate invasion "Vmf" for a given thickness at said each unit of depth in said wellbore in response to the determination of said volume of mud filtrate invasion Vmf into said flushed zone and said transition zone by said first means.

3. A method of generating an output record medium illustrating a characteristic of a formation traversed by a wellbore, said formation having permeable zones, comprising the steps of generating by a well tool in a wellbore, output signals characteristic of a formation traversed by said wellbore:

receiving said output signals representative of a set of invasion parameters for each unit of depth in said wellbore;

for a given thickness at said each unit of depth in said wellbore, determining from said invasion parameters a volume of mud filtrate which has invaded into the permeable zones of said formation traversed by said wellbore, the determining step including the step of further determining said volume of mud filtrate which has invaded into the permeable zones of said formation traversed by said wellbore for a given thickness at said each unit of depth in said wellbore by using the following equation;

space="preserve" listing-type="equation">Vmf=3.1416 . . . /3[(Rmf/Rxo).sup.1/n ][r.sub.1.sup.2 +(r.sub.1)(r.sub.2)+r.sub.2.sup.2 -3r.sub.b.sup.2 ],

where Vmf is the volume of mud filtrate, Rxo is a resistivity of a flushed zone in said formation, Rmf is the resistivity of said mud filtrate, r₁ is a radius measured from a wall of said wellbore to an outer radial extremity of said flushed zone, r₂ is a radius measured from a wall of said wellbore to an inner radial extremity of an uninvaded zone in said formation, and r_b is a radius of said wellbore; and

plotting the volume of mud filtrate invasion into the permeable zones of said formation for said each unit of depth on said output record medium.

4. The method of claim 3, wherein the plotting step comprises the step of:

displaying said Vmf representing the volume of mud filtrate invasion into said formation for said each unit of depth of said wellbore on a graph, a collection of said Vmf over a corresponding collection of depths in said wellbore representing said output record medium.

5. In a system including a well tool adapted to be disposed in a wellbore for generating output signals characteristic of a formation traversed by said wellbore and a surface apparatus adapted to be disposed at a surface of said wellbore and responsive to said output signals for generating an output record medium illustrating said characteristics of said formation, said surface apparatus including first means responsive to said output signals for generating invasion parameters associated with each unit of depth in said wellbore representative of a plurality of permeable zones in said formation and second means responsive to said invasion parameters for generating said output record medium illustrating a volume of mud filtrate invasion into said zones of said formation traversed by said wellbore, said second means comprising:

mud filtrate volume determination means responsive to said invasion parameters associated with said each unit of depth in said wellbore for determining a corresponding volume of mud filtrate which has invaded into said permeable zones of said formation for a given thickness at said each unit of depth in said wellbore,

said permeable zones of said formation at each depth in said wellbore including a flushed zone, an uninvaded zone, and a transition zone interposed between said flushed zone and said uninvaded zone,

said invasion parameters including a resistivity of the flushed zone (Rxo), a radius (r₁) measured from a wall of said wellbore to an outer radial extremity of said flushed zone, and a radius (r₂) measured from a wall of said wellbore to an inner radial extremity of said uninvaded zone,

said mud filtrate volume determination means determining said volume of mud filtrate invasion into said flushed zone and said transition zone of said formation for a given thickness at said each unit of depth in said wellbore by using the following equation;

space="preserve" listing-type="equation">Vmf=3.1416 . . . /3[(Rmf/Rxo).sup.1/n ][r.sub.1.sup.2 +(r.sub.1)(r.sub.2)+r.sub.2.sup.2 3r.sub.b.sup.2 ],

where Vmf is the volume of mud filtrate, Rmf is the resistivity of said mud filtrate, and r_b is the radius of said wellbore; and

output record generating means responsive to the volume of mud filtrate invasion into said permeable zones of said formation for a given thickness at said each unit of depth in said wellbore determined by said mud filtrate volume determination means for generating an output record medium illustrating said volume of mud filtrate which has invaded into said permeable zones of said formation at a given thickness for said each unit of depth in the wellbore.

6. In the system of claim 5, wherein said output record generating means generates said output record medium, said output record medium illustrating said volume of mud filtrate "Vmf" which has invaded into the flushed zone and the transition zone of said formation for a given thickness at said each unit of depth in said wellbore in response to the determination of the volume of mud filtrate invasion Vmf into said flushed zone and said transition zone by said mud filtrate volume determination means.

7. In the system of claim 6, wherein said first means comprises:

borehole correction means responsive to said output signals for correcting said output signals to eliminate the effect of the presence of said wellbore and generating a set of corrected output signals;

signal processing means responsive to said set of corrected output signals from said borehole correction means for further processing said output signals thereby generating processed and corrected output signals; and

parameterization means responsive to the processed and corrected output signals from said signal processing means for generating said invasion parameters associated with each unit of depth in said wellbore representative of said flushed zone, said transition zone, and said uninvaded zone in said formation traversed by said wellbore.

8. In a system including a well tool adapted to be disposed in a wellbore for generating output signals characteristic of a formation traversed by said wellbore and a surface apparatus adapted to be disposed at a surface of said wellbore and responsive to said output signals for generating an output record medium illustrating said characteristics of said formation, said surface apparatus including first means responsive to said output signals for generating invasion parameters associated with each unit of depth in said wellbore representative of a plurality of zones in said formation and second means responsive to said invasion parameters for generating said output record medium illustrating a volume of mud filtrate invasion into said zones of said formation traversed by said wellbore, a method practiced by said second means for generating said output record medium, comprising the steps of:

receiving in said second means said invasion parameters for each unit of depth in said wellbore;

for a given thickness at said each unit of depth in said wellbore, in response to said invasion parameters, determining a volume of mud filtrate which has invaded into said zones of said formation for a given thickness at said each unit of depth in said wellbore, the determining step including the step of further determining said volume of mud filtrate which has invaded the zones of said formation for a given thickness at said each unit of depth in said wellbore by using the following equation;

space="preserve" listing-type="equation">Vmf=3.1416 . . . /3[(Rmf/Rxo).sup.1/n ][r.sub.1.sup.2 +(r.sub.1)(r.sub.2)+r.sub.2.sup.2 -3r.sub.b.sup.2 ],

where Vmf is the volume of mud filtrate, Rxo is a resistivity of a flushed zone in said formation, Rmf is the resistivity of said mud filtrate, r₁ is a radius measured from a wall of said wellbore to an outer radial extremity of said flushed zone, r₂ is a radius measured from a wall of said wellbore to an inner radial extremity of an uninvaded zone in said formation, and r_b is a radius of said wellbore; and

plotting the volume of mud filtrate invasion in said zones of said formation on said output record medium.

9. A system for generating an output record medium illustrating a volume of mud filtrate invasion into permeable zones of a formation penetrated by a wellbore at each unit of depth in said wellbore, comprising:

first means for determining a corresponding volume of mud filtrate which has invaded into said permeable zones including a flushed zone, an uninvaded zone and a transition zone of said formation traversed by said wellbore for a given thickness at said each unit of depth in said wellbore in response to a set of invasion parameters, the invasion parameters including a resistivity of the flushed zone (Rxo), a radius (r₁) measured from a wall of said wellbore to an outer radial extremity of said flushed zone, and a radius (r₂) measured from a wall of said wellbore to an inner radial extremity of said uninvaded zone, said first means determining the volume of mud filtrate invasion into said flushed zone and said transition zone of said formation for a given thickness at said each unit of depth in said wellbore by using the following equation;

space="preserve" listing-type="equation">Vmf=3.1416 . . . /3[(Rmf/Rxo).sup.1/n ][r.sub.1.sup.2 +(r.sub.1)(r.sub.2)+r.sub.2.sup.2 -3r.sub.b.sup.2 ],

where Vmf is the volume of mud filtrate, Rmf is a resistivity of said mud filtrate, and r_b is a radius of said wellbore; and

output record generating means responsive to the volume of mud filtrate invasion determined by said first means for generating said output record medium illustrating said volume of mud filtrate invasion into said permeable zones of said formation at said each unit of depth in the wellbore.

10. A method of generating an output record medium illustrating a characteristic of a formation traversed by a wellbore, said formation having permeable zones, comprising the steps of generating by a well tool in a wellbore, output signals characteristic of a formation traversed by said wellbore;

receiving said output signals representative of a set of invasion parameters for each unit of depth in said wellbore;

for a given thickness at said each unit of depth in said wellbore, determining from said invasion parameters a volume of mud filtrate which has invaded into said permeable zones of said formation for a given thickness at said each unit of depth in said wellbore by using the following equation;

space="preserve" listing-type="equation">Vmf=3.1416 . . . /3[(Rmf/Rxo).sup.1/n ][r.sub.1.sup.2 +(r.sub.1)(r.sub.2)+r.sub.2.sup.2 -3r.sub.b.sup.2 ],

where Vmf is the volume of mud filtrate, Rxo is a resistivity of a flushed zone in said formation, Rmf is a resistivity of said mud filtrate, r₁ is a radius measured from a wall of said wellbore to an outer radial extremity of said flushed zone, r₂ is a radius measured from a wall of said wellbore to an inner radial extremity of an uninvaded zone in said formation, and r_b is a radius of said wellbore; and

plotting said volume of mud filtrate which has invaded into the permeable zones of said formation for said each unit of depth on said output record medium.