Method and apparatus for cementing drill strings in place for one pass drilling and completion of oil and gas wells

The steel drill string attached to a drilling bit during typical rotary drilling operations used to drill oil and gas wells is used for a second purpose as the casing that is cemented in place during typical oil and gas well completions. Methods of operation are described that provide for the efficient installation a cemented steel cased well wherein the drill string and the drill bit are cemented into place during one single drilling pass down into the earth. The normal mud passages or watercourses present in the rotary drill bit are used for the second independent purpose of passing cement into the annulus between the casing and the well while cementing the drill string into place during one single pass into the earth. A one-way cement valve is installed near the drill bit of the drill string that allows the cement to set up efficiently under ambiently hydrostatic conditions while the drill string and drill bit are cemented into place during one single drilling pass into the earth.

Portions of this application were disclosed in U.S. Disclosure Document No. 
362582 filed on Sep. 30, 1994 which is incorporated herein by reference. 
BACKGROUND OF THE INVENTION 
1. Field of Invention 
The field of invention relates to apparatus that uses the steel drill 
string attached to a drilling bit during drilling operations used to drill 
oil and gas wells for a second purpose as the casing that is cemented in 
place during typical oil and gas well completions. The field of invention 
further relates to methods of operation of said apparatus that provides 
for the efficient installation a cemented steel cased well during one 
single pass down into the earth of the steel drill string. The field of 
invention further relates to methods of operation of the apparatus that 
uses the typical mud passages already present in a typical drill bit, 
including any watercourses in a "regular bit", or mud jets in a "jet bit", 
that allow mud to circulate during typical drilling operations for the 
second independent, and the distinctly separate, purpose of passing cement 
into the annulus between the casing and the well while cementing the drill 
string into place during one single drilling pass into the earth. The 
field of invention further relates to apparatus and methods of operation 
that provides the pumping of cement down the drill string, through the mud 
passages in the drill bit, and into the annulus between the formation and 
the drill string for the purpose of cementing the drill string and the 
drill bit into place during one single drilling pass into the formation. 
The field of invention further relates to a one-way cement valve and 
related devices installed near the drill bit of the drill string that 
allows the cement to set up efficiently while the drill string and drill 
bit are cemented into place during one single drilling pass into the 
formation. 
2. Description of the Prior Art 
At the time of the filing of the application herein, the applicant is 
unaware of any prior art that is particularly relevant to the invention. 
SUMMARY OF THE INVENTION 
Apparatus and methods of operation of that apparatus are disclosed that 
allow for cementation of a drill string with attached drill bit into place 
during one single drilling pass into a geological formation. The process 
of drilling the well and installing the casing becomes one single process 
that saves installation time and reduces costs during oil and gas well 
completion procedures. Apparatus and methods of operation of the apparatus 
are disclosed that use the typical mud passages already present in a 
typical rotary drill bit, including any watercourses in a "regular bit", 
or mud jets in a "jet bit", for the second independent purpose of passing 
cement into the annulus between the casing and the well while cementing 
the drill string in place. This is a crucial step that allows a "Typical 
Drilling Process" involving some 14 steps to be compressed into the "New 
Drilling Process" that involves only 7 separate steps as described in the 
Description of the Preferred Embodiments below. The New Drilling Process 
is now possible because of "Several Recent Changes in the Industry" also 
described in the Description of the Preferred Embodiments below. In 
addition, the New Drilling Process also requires new apparatus to properly 
allow the cement to cure under ambient hydrostatic conditions. That new 
apparatus includes a Latching Subassembly, a Latching Float Collar Valve 
Assembly, the Bottom Wiper Plug, and the Top Wiper Plug. Suitable methods 
of operation are disclosed for the use of the new apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Apparatus and methods of operation of that apparatus are disclosed herein 
in the preferred embodiments of the invention that allow for cementation 
of a drill string with attached drill bit into place during one single 
drilling pass into a geological formation. The method of drilling the well 
and installing the casing becomes one single process that saves 
installation time and reduces costs during oil and gas well completion 
procedures as documented in the following description of the preferred 
embodiments of the invention. Apparatus and methods of operation of the 
apparatus are disclosed herein that use the typical mud passages already 
present in a typical rotary drill bit, including any watercourses in a 
"regular bit", or mud jets in a "jet bit", for the second independent 
purpose of passing cement into the annulus between the casing and the well 
while cementing the drill string in place. 
FIG. 1 shows a section view of a drill string in the process of being 
cemented in place during one drilling pass into formation. A borehole 2 is 
drilled though the earth including geological formation 4. The borehole is 
drilled with a milled tooth rotary drill bit 6 having milled steel roller 
cones 8, 10, and 12 (not shown for simplicity). A standard water passage 
14 is shown through the rotary cone drill bit. This rotary bit could 
equally be a tungsten carbide insert roller cone bit having jets for 
waterpassages, the principle of operation and the related apparatus being 
the same for either case for the preferred embodiment herein. 
The threads 16 on rotary drill bit 6 are screwed into the Latching 
Subassembly 18. The Latching Subassembly is also called the Latching Sub 
for simplicity herein. The Latching Sub is a relatively thick-walled steel 
pipe having some functions similar to a standard drill collar. 
The Latching Float Collar Valve Assembly 20 is pumped downhole with 
drilling mud after the depth of the well is reached. The Latching Float 
Collar Valve Assembly is pumped downhole with mud pressure pushing against 
the Upper Seal 22 of the Latching Float Collar Valve Assembly. The 
Latching Float Collar Valve Assembly latches into place into Latch 
Recession 24. The Latch 9.6 of the Latching Float Collar Valve Assembly is 
shown latched into place with Latching Spring 28 pushing against Latching 
Mandrel 30. 
The Float 32 of the Latching Float Collar Valve Assembly seats against the 
Float Seating Surface 34 under the force from Float Collar Spring 36 that 
makes a one-way cement valve. However, the pressure applied to the mud or 
cement from the surface may force open the Float to allow mud or cement to 
be forced into the annulus generally designated as 38 in FIG. 1. This 
one-way cement valve is a particular example of "a one-way cement valve 
means installed near the drill bit" which is a term defined herein. The 
one-way cement valve means may be installed at any distance from the drill 
bit but is preferentially installed "near" the drill bit. 
FIG. 1 corresponds to the situation where cement is in the process of being 
forced from the surface through the Latching Float Collar Valve Assembly. 
In fact, the top level of cement in the well is designated as element 40. 
Below 40, cement fills the annulus of the borehole. Above 40, mud fills 
the annulus of the borehole. For example, cement is present at position 42 
and drilling mud is present at position 44 in FIG. 1. 
Relatively thin-wall casing, or drill pipe, designated as element 46 in 
FIG. 1, is attached to the Latching Sub. The bottom male threads of the 
drill pipe 48 are screwed into the female threads 50 of the Latching Sub. 
The drilling mud was wiped off the walls of the drill pipe in the well with 
Bottom Wiper Plug 52. The Bottom Wiper Plug is fabricated from rubber in 
the shape shown. Portions 54 and 56 of the Upper Seal of the Bottom Wiper 
Plug are shown in a ruptured condition in FIG. 1. Initially, they sealed 
the upper portion of the Bottom Wiper Plug. Under pressure from cement, 
the Bottom Wiper Plug is pumped down into the well until the Lower Lobe of 
the Bottom Wiper Plug 58 latches into place into Latching Sub Recession 60 
in the Latching Sub. After the Bottom Wiper Plug latches into place, the 
pressure of the cement ruptures The Upper Seal of the Bottom Wiper Plug. A 
Bottom Wiper Plug Lobe 62 is shown in FIG. 1. Such lobes provide an 
efficient means to wipe the mud off the walls of the drill pipe while the 
Bottom Wiper Plug is pumped downhole with cement. 
Top Wiper Plug 64 is being pumped downhole by water 66 under pressure in 
the drill pipe. As the Top Wiper Plug 64 is pumped down under water 
pressure, the cement remaining in region 68 is forced downward through the 
Bottom Wiper Plug, through the Latching Float Collar Valve Assembly, 
through the waterpassages of the drill bit and into the annulus in the 
well. A Top Wiper Plug Lobe 70 is shown in FIG. 1. Such lobes provide an 
efficient means to wipe the cement off the walls of the drill pipe while 
the Top Wiper Plug is pumped downhole with water. 
After the Bottom Surface 72 of the Top Wiper Plug is forced into the Top 
Surface 74 of the Bottom Wiper Plug, almost the entire "cement charge" has 
been forced into the annulus between the drill pipe and the hole. As 
pressure is reduced on the water, the Float of the Latching Float Latching 
Float Collar Valve Assembly seals against the Float Seating Surface. As 
the water pressure is reduced on the inside of the drill pipe, then the 
cement in the annulus between the drill pipe and the hole can cure under 
ambient hydrostatic conditions. This procedure herein provides an example 
of the proper operation of a "one-way cement valve means". 
Therefore, the preferred embodiment in FIG. 1 provides apparatus that uses 
the steel drill string attached to a drilling bit during drilling 
operations used to drill oil and gas wells for a second purpose as the 
casing that is cemented in place during typical oil and gas well 
completions. 
The preferred embodiment in FIG. 1 provides apparatus and methods of 
operation of said apparatus that results in the efficient installation a 
cemented steel cased well during one single pass down into the earth of 
the steel drill string thereby making a steel cased borehole or cased 
well. 
The steps described herein in relation to the preferred embodiment in FIG. 
1 provides a method of operation that uses the typical mud passages 
already present in a typical rotary drill bit, including any watercourses 
in a "regular bit", or mud jets in a "jet bit", that allow mud to 
circulate during typical drilling operations for the second independent, 
and the distinctly separate, purpose of passing cement into the annulus 
between the casing and the well while cementing the drill string into 
place during one single pass into the earth. 
The preferred embodiment of the invention further provides apparatus and 
methods of operation that results in the pumping of cement down the drill 
string, through the mud passages in the drill bit, and into the annulus 
between the formation and the drill string for the purpose of cementing 
the drill string and the drill bit into place during one single drilling 
pass into the formation. 
The apparatus described in the preferred embodiment in FIG. 1 also provide 
a one-way cement valve and related devices installed near the drill bit of 
the drill string that allows the cement to set up efficiently while the 
drill string and drill bit are cemented into place during one single 
drilling pass into the formation. 
Methods of operation of apparatus disclosed in FIG. 1 have been disclosed 
that use the typical mud passages already present in a typical rotary 
drill bit, including any watercourses in a "regular bit", or mud jets in a 
"jet bit", for the second independent purpose of passing cement into the 
annulus between the casing and the well while cementing the drill string 
in place. This is a crucial step that allows a "Typical Drilling Process" 
involving some 14 steps to be compressed into the "New Drilling Process" 
that involves only 7 separate steps as described in detail below. The New 
Drilling Process is now possible because of "Several Recent Changes in the 
Industry" also described in detail below. 
Typical procedures used in the oil and gas industries to drill and complete 
wells are well documented. For example, such procedures are documented in 
the entire "Rotary Drilling Series" published by the Petroleum Extension 
Service of the University of Texas at Austin, Austin, Tex. that is 
included herein by reference in its entirety comprised of the following: 
Unit I--"The Rig and Its Maintenance" (12 Lessons); Unit II--"Normal 
Drilling Operations" (5 Lessons); Unit III--Nonroutine Rig Operations (4 
Lessons); Unit IV--Man Management and Rig Management (1 Lesson); and Unit 
V--Offshore Technology (9 Lessons). All of the individual Glossaries of 
all of the above Lessons are explicitly included in the specification 
herein and any and all definitions in those Glossaries shall be considered 
explicitly referenced herein. 
Additional procedures used in the oil and gas industries to drill and 
complete wells are well documented in the series entitled "Lessons in Well 
Servicing and Workover" published by the Petroleum Extension Service of 
the University of Texas at Austin, Austin, Tex. that is included herein by 
reference in its entirety comprised of all 12 Lessons. All of the 
individual Glossaries of all of the above Lessons are explicitly included 
in the specification herein and any and all definitions in those 
Glossaries shall be considered explicitly referenced herein. 
With reference to typical practices in the oil and gas industries, a 
typical drilling process may therefore be described in the following. 
Typical Drilling Process 
From an historical perspective, completing oil and gas wells using rotary 
drilling techniques have in recent times comprised the following typical 
steps: 
Step 1 
With a pile driver or rotary rig, install any necessary conductor pipe on 
the surface for attachment of the blowout preventer and for mechanical 
support at the wellhead. 
Step 2 
Install and cement into place any surface casing necessary to prevent 
washouts and cave-ins near the surface, and to prevent the contamination 
of freshwater sands as directed by state and federal regulations. 
Step 3 
Choose the dimensions of the drill bit to result in the desired sized 
production well. Begin rotary drilling of the production well with a first 
drill bit. Simultaneously circulate drilling mud into the well while 
drilling. Drilling mud is circulated downhole to carry rock chips to the 
surface, to prevent blowouts, to prevent excessive mud loss into 
formation, to cool the bit, and to clean the bit. After the first bit 
wears out, pull the drill string out, change bits, lower the drill string 
into the well and continue drilling. It should be noted here that each 
"trip" of the drill bit typically requires many hours of rig time to 
accomplish the disassembly and reassembly of the drill string, pipe 
segment by pipe segment. 
Step 4 
Drill the production well using a succession of rotary drill bits attached 
to the drill string until the hole is drilled to its final depth. 
Step 5 
After the final depth is reached, pull out the drill string and its 
attached drill bit. 
Step 6 
Perform open-hole logging of the geological formations to determine the 
amount of oil and gas present. This typically involves measurements of the 
porosity of the rock, the electrical resistivity of the water present, the 
electrical resistivity of the rock, certain neutron measurements from 
within the open-hole, and the use of Archie's Equations. If no oil and gas 
is present from the analysis of such open-hole logs, an option can be 
chosen to cement the well shut. If commercial amounts of oil and gas are 
present, continue the following steps. 
Step 7 
Typically reassemble drill bit and drill string into the well to clean the 
well after open-hole logging. 
Step 8 
Pull out the drill string and its attached drill bit. 
Step 9 
Attach the casing shoe into the bottom male pipe threads of the first 
length of casing to be installed into the well. This casing shoe may or 
may not have a one-way valve ("casing shoe valve") installed in its 
interior to prevent fluids from back-flowing from the well into the casing 
string. 
Step 10 
Typically install the float collar onto the top female threads of the first 
length of casing to be installed into the well which has a one-way valve 
("float collar valve") that allows the mud and cement to pass only one way 
down into the hole thereby preventing any fluids from back-flowing from 
the well into the casing string. Therefore, a typical installation has a 
casing shoe attached to the bottom and the float collar valve attached to 
the top portion of the first length of casing to be lowered into the well. 
Please refer to pages 28-31 of the book entitled "Casing and Cementing" 
Unit II Lesson 4, Second Edition, of the Rotary Drilling Series, Petroleum 
Extension Service, The University of Texas at Austin, Tex., 1982 
(hereinafter defined as "Ref.1"). All of the individual definitions of 
words and phrases in the Glossary of Ref. 1 are explicitly included herein 
in their entirety. 
Step 11 
Assemble and lower the production casing into the well while back filling 
each section of casing with mud as it enters the well to overcome the 
buoyancy effects of the air filled casing (caused by the presence of the 
float collar valve), to help avoid sticking problems with the casing, and 
to prevent the possible collapse of the casing due to accumulated build-up 
of hydrostatic pressure. 
Step 12 
To "cure the cement under ambient hydrostatic conditions", typically 
execute a two-plug cementing procedure involving a first Bottom Wiper Plug 
before and a second Top Wiper Plug behind the cement that also minimizes 
cement contamination problems comprised of the following individual steps: 
A. Introduce the Bottom Wiper Plug into the interior of the steel casing 
assembled in the well and pump down with cement that cleans the mud off 
the walls and separates the mud and cement (Ref. 1, pages 28-31). 
B. Introduce the Top Wiper Plug into the interior of the steel casing 
assembled into the well and pump down with water under pump pressure 
thereby forcing the cement through the float collar valve and any other 
one-way valves present (Ref. 1, pages 28-31). 
C. After the Bottom Wiper Plug and the Top Wiper Plug have seated in the 
float collar, release the pump pressure on the water column in the casing 
that results in the closing of the float collar valve which in turn 
prevents cement from backing up into the interior of the casing. The 
resulting interior pressure release on the inside of the casing upon 
closure of the float collar valve prevents distortions of the casing that 
might prevent a good cement seal (Ref. 1, page 30). In such circumstances, 
"the cement is cured under ambient hydrostatic conditions". 
Step 13 
Allow the cement to cure. 
Step 14 
Follow normal "final completion operations" that include installing the 
tubing with packers and perforating the casing near the producing zones. 
For a description of such normal final completion operations, please refer 
to the book entitled "Well Completion Methods", Well Servicing and 
Workover, Lesson 4, from the series entitled "Lessons in Well Servicing 
and Workover", Petroleum Extension Service, The University of Texas at 
Austin, Tex., 1971 (hereinafter defined as "Ref. 2"). All of the 
individual definitions of words and phrases in the Glossary of Ref. 2 are 
explicitly included herein in their entirety. Other methods of completing 
the well are described therein that shall, for the purposes of this 
application herein, also be called "final completion operations". 
Several Recent Changes in the Industry 
Several recent concurrent changes in the industry have made it possible to 
reduce the number of steps defined above. These changes include the 
following: 
a. Until recently, drill bits typically wore out during drilling operations 
before the desired depth was reached by the production well. However, 
certain drill bits have recently been able to drill a hole without having 
to be changed. For example, please refer to the book entitled "The Bit", 
Unit I, Lesson 2, Third Edition, of the Rotary Drilling Series, The 
University of Texas at Austin, Tex., 1981 (hereinafter defined as "Ref. 
3"). All of the individual definitions of words and phrases in the 
Glossary of Ref. 3 are explicitly included herein in their entirety. On 
page 1 of Ref. 3 it states: "For example, often only one bit is needed to 
make a hole in which the casing will be set." On page 12 of Ref. 3 it 
states in relation to tungsten carbide insert roller cone bits: "Bit runs 
as long as 300 hours have been achieved; in some instances, only one or 
two bits have been needed to drill a well to total depth." This is 
particularly so since the advent of the sealed bearing tri-cone bit 
designs appeared in 1959 (Ref. 3, page 7) having tungsten carbide inserts 
(Ref. 3, page 12). Therefore, it is now practical to talk about drill bits 
lasting long enough for drilling a well during one pass into the 
formation, or "one pass drilling". 
b. Until recently, it has been impossible or impractical to obtain 
sufficient geophysical information to determine the presence or absence of 
oil and gas from inside steel pipes in wells. Heretofore, either standard 
open-hole logging tools or Measurement-While-Drilling ("MWD") tools were 
used in the open-hole to obtain such information. Therefore, the industry 
has historically used various open-hole tools to measure formation 
characteristics. However, it has recently become possible to measure the 
various geophysical quantities listed in Step 6 above from inside steel 
pipes such as drill strings and casing strings. For example, please refer 
to the book entitled "Cased Hole Log Interpretation 
Principles/Applications", Schlumberger Educational Services, Houston, 
Tex., 1989. Please also refer to the article entitled "Electrical Logging: 
State-of-the-Art", by Robert E. Maute, The Log Analyst, May-June 1992, 
pages 206-227. 
Because drill bits typically wore out during drilling operations until 
recently, different types of metal pipes have historically evolved which 
are attached to drilling bits, which, when assembled, are called "drill 
strings". Those drill strings are different than typical "casing strings" 
run into the well. Because it was historically absolutely necessary to do 
open-hole logging to determine the presence or absence of oil and gas, the 
fact that different types of pipes were used in "drill strings" and 
"casing strings" was of little consequence to the economics of completing 
wells. However, it is possible to choose the "drill string" to be 
acceptable for a second use, namely as the "easing string" that is to be 
installed after drilling has been completed. 
New Drilling Process 
Therefore, the preferred embodiments of the invention herein reduces and 
simplifies the above 14 steps as follows: 
EQU Repeat Steps 1-2 above. 
Steps 3-5 (Revised) 
Choose the drill bit so that the entire production well can be drilled to 
its final depth using only one single drill bit. Choose the dimensions of 
the drill bit for desired size of the production well. If the cement is to 
be cured under ambient hydrostatic conditions, attach the drill bit to the 
bottom female threads of the Latching Subassembly ("Latching Sub"). Choose 
the material of the drill string from pipe material that can also be used 
as the casing string. Attach the first section of drill pipe to the top 
female threads of the Latching Sub. Rotary drill the production well to 
its final depth during "one pass drilling" into the well. While drilling, 
simultaneously circulate drilling mud to carry the rock chips to the 
surface, to prevent blowouts, to prevent excessive mud loss into 
formation, to cool the bit, and to clean the bit. 
Step 6 (Revised) 
After the final depth of the production well is reached, perform logging of 
the geological formations to determine the amount of oil and gas present 
from inside the drill pipe of the drill string. This typically involves 
measurements from inside the drill string of the necessary geophysical 
quantities as summarized in Item "b." of "Several Recent Changes in the 
Industry". If such logs obtained from inside the drill string show that no 
oil or gas is present, then the drill string can be pulled out of the well 
and the well filled in with cement. If commercial amounts of oil and gas 
are present, continue the following steps. 
Steps 7-11 (Revised) 
If the cement is to be cured under ambient hydrostatic conditions, pump 
down a Latching Float Collar Valve Assembly with mud until it latches into 
place in the notches provided in the Latching Sub located above the drill 
bit. 
Steps 12-13 (Revised) 
To "cure the cement under ambient hydrostatic conditions", typically 
execute a two-plug cementing procedure involving a first Bottom Wiper Plug 
before and a second Top Wiper Plug behind the cement that also minimizes 
cement contamination comprised of the following individual steps: 
A. Introduce the Bottom Wiper Plug into the interior of the drill string 
assembled in the well and pump down with cement that cleans the mud off 
the walls and separates the mud and cement. 
B. Introduce the Top Wiper Plug into the interior of the drill string 
assembled into the well and pump down with water thereby forcing the 
cement through any Float Collar Valve Assembly present and through the 
watercourses in "a regular bit" or through the mud nozzles of a "jet bit" 
or through any other mud passages in, the drill bit into the annulus 
between the drill string and the formation. 
C. After the Bottom Wiper Plug, and Top Wiper Plug have seated in the 
Latching Float Collar Valve Assembly, release the pressure on the interior 
of the drill string that results in the closing of the float collar which 
in turn prevents cement from backing up in the drill string. The resulting 
pressure release upon closure of the float collar prevents distortions of 
the drill string that might prevent a good cement seal as described 
earlier. Ie, "the cement is cured under ambient hydrostatic conditions". 
Repeat Step 14 above. 
Therefore, the "New Drilling Process" has only 7 distinct steps instead of 
the 14 steps in the "Typical Drilling Process". The "New Drilling 
Process", consequently has fewer steps, is easier to implement, and will 
be less expensive. 
The preferred embodiment of the invention disclosed in FIG. 1 requires a 
Latching Subassembly and a Latching Float Collar Valve Assembly. The 
advantage of this approach is that the Float 32 of the Latching Float 
Collar Valve Assembly and the Float Seating Surface 34 in FIG. 1 are 
installed at the end of the drilling process and will not be worn due to 
mud passage during normal drilling operations. 
Another preferred embodiment of the invention provides a float and float 
collar valve assembly permanently installed within the Latching 
Subassembly at the beginning of the drilling operations. However, such a 
preferred embodiment has the disadvantage that drilling mud passing by the 
float and the float collar valve assembly during normal drilling 
operations will tend to wear on the mutually sealing surfaces. 
The drill bit described in FIG. 1 is a milled steel toothed roller cone 
bit. However, any rotary bit can be used with the invention. A tungsten 
carbide insert roller cone bit can be used. Any type of diamond bit or 
drag bit can be used. The invention may be used with any drill bit 
described in Ref. 3 above that possesses mud passages, waterpassages, or 
passages for gas. Any type of rotary drill bit can be used possessing such 
passageways. Similarly, any type of bit whatsoever that utilizes any fluid 
or gas that passes through passageways in the bit can be used whether or 
not the bit rotates. 
While the above description contains many specificities, these should not 
be construed as limitations on the scope of the invention, but rather as 
exemplification of preferred embodiments thereto. As have been briefly 
described, there are many possible variations. Accordingly, the scope of 
the invention should be determined not only by the embodiments 
illustrated, but by the appended claims and their legal equivalents.