The document summarizes the key requirements of the Texas Railroad Commission's Statewide Rule 13 regarding well casing and cementing. It outlines the pressure testing requirements for surface, intermediate, and production casing strings. It also details the cement height requirements to isolate usable quality water and seal off productive zones and injection wells. The rule aims to ensure casing controls the well and isolates water by implementing rigorous testing and cementing standards.

1. Feeling the Pressure on Drilling and Completions? :
Well Structure Compliance with Texas Railroad Commission’s Statewide Rule 13
By Logan Lewis, TAEP Government Relations Intern
Drilling a well in the state of Texas. Yup, you all know what I’m talking about, and you are no
doubt familiar with Statewide Rule 13. The Texas Railroad Commission (RRC) recently updated the rule
for the first time in nearly thirty years. The Commission adapted the rule in an effort to tailor the
legislation to account for new technological advances in the industry, but it still adheres to the same
vision as when it was first drafted: ensuring that casing effectively controls the well, isolating all useable
quality water and sealing off all “trouble” zones to ensure no fluid can vertically migrate behind the
casing.
Statewide Rule 13 now details the requirements on everything from drilling fluid regimes and
well control to casing testing and hydraulic fracturing. Not only is it expansive; it is also notoriously
difficult to follow. A few of the most commonly applied topics in Statewide Rule 13 pertain to the
regulations surrounding the pressure testing of casing and the placement of cement. With any luck, this
article will clear up some common misconceptions on these topics and to plainly outline the
requirements presented in the rule.
Rule 13 places immense value on protecting the useable quality ground water located near the
surface (Don’t we all?). This is accomplished by implementing rigorous quality control around setting
and testing the surface casing string. Before operators can even begin to set the casing string, two key
documents are needed: a letter obtained from the Groundwater Advisory Unit of the Oil and Gas
Division and the pipe test documentation. The letter from the Groundwater Advisory Unit specifies the
protection depth that the surface casing must meet to conserve the fresh water strata. The pipe test
documentation consists of either a mill test report for new pipe, or a refurbished pipe report for used
pipe. These reports state that the casing has either been hydrostatically pressure tested or gauged with
a casing evaluation tool and can withstand the maximum downhole pressure. Together, these
documents are meant to prove that the well structure is capable of effectively sealing the protection
zone and should be kept on hand throughout the operation.
Once the operator sets the casing and pumps adequate cement to fill the annular space from
the shoe to the surface, and before drilling the plug out, they assess the casing using a mechanical
integrity test. The operator must test the casing at a pump pressure of 0.5 psi × total vertical depth for
30 minutes. This pressure does not need to exceed 1500 psi. If the pressure drops more than 10% in this
time period, the test is failed, and all operations are suspended until the RRC district director approves a
remediation plan.
After drilling commences through the plug and to the depth of the next casing string, there is a
possibility that the surface casing string may need to be tested once more (obviously, we like to protect
our fresh water). Rule 13 states that if the surface casing is exposed to more than 360 rotating hours,
the string’s integrity must be proven by another hydrostatic pressure test, use of a casing evaluation
tool, or another RRC approved method. The key phrase to notice in this clause is “rotating hours,”
meaning that the time spent tripping in and out of the well is excluded from the net rotating time. In the
event that operators do exceed 360 rotating hours, the testing proceeds in the same manner as the
original test – however, the RRC requests an eight-hour notice to give the district office an opportunity
to witness the test and the outcome.

2. The intermediate and production casing strings follow identical testing procedures to those of
the surface casing. The same cannot be said for the regulations pertaining to the cement height
requirements. Hoping to detail a wide range of acceptable practices, the legislature devotes an
extensive list of guidelines on determining the top of cement. While this doesn’t make Statewide Rule
13 a lighter read, it does give the operator a bit of autonomy in regards to economics, while still
complying with RRC regulations.
As a standard, each string of casing must be cemented from the shoe to a point 600 feet above
the shoe. That’s the easy part. If and when an operator encounters a “trouble zone” (a productive zone,
potential flow zone, or a zone with corrosive fluid), the rule opens up a margin for operator
interpretation. If the operator plans on sealing off the trouble zone by determining the top of cement by
calculation, the casing must be cemented from the shoe to at least 600 feet above the top of the
shallowest trouble zone. If the operator uses a temperature survey, the cement must rise to 250 feet
above the trouble zone; a cement evaluation log warrants 100-foot rise above the zone and if all else
fails, the cement must rise to at least 200 feet above the shoe of the next casing string. If these
requirements prove impossible or ineffective, the RRC district director can approve alternate cementing
plans and certain multi-stage processes.
Another recent addition to the rule involves injection and disposal zones. In order to
compensate for possible increases of formation pressure and to prevent unwanted fluid from entering
the annulus, casing must be cemented across and above all formations permitted for injections wells
operating within a ¼ mile radius. In the event of an EOR project, the operator must cement the casing
above all formations permitted for injection into productive reservoirs. In both cases, the cement height
is determined using the guidelines for the trouble zones mentioned above.
Finally, the RRC made a significant amendment to Rule 13 concerning hydraulic fracturing
treatments. A minimum internal yield pressure of at least 1.10 times the maximum pressure of the
completion method is Rule 13-standard for any casing string or tubing installed in a well subjected to a
hydraulic fracturing treatment. If the operator included a pressure actuated valve or sleeve in their well
design, the device only needs to be tested at 80% of the actuation pressure for 5 minutes. The total test
of the casing from the wellhead to the top of cement behind the casing concerned is considered a failure
if the original pressure drops by more than 10%. If the test is deemed a failure, the operator must obtain
an RRC-approved remediation plan before the treatment can proceed. This is also relevant if any
abnormal pressure increases are observed in the annulus. As a result, it is exceedingly important that
operators monitor all annuli throughout the treatment operation.
The Texas Railroad Commission spared no attention to detail when outlining well structure in
Statewide Rule 13. They hit every topic from drilling fluid regimes and well control to casing testing and
hydraulic fracturing, all the while reflecting back on the purpose of the rule. By following the regulations
laid out Rule 13 and explained in this article, operators should have little trouble in ensuring that casing
effectively controls the well, seals off all trouble zones, and ultimately isolates and protects all useable
quality water. Hopefully the requirements outlined in the Texas Railroad Commission’s Statewide Rule
13 are now a bit clearer than your average drilling fluid, and we can all get back to drilling for oil!

3. Casing String Pressure Testing Requirements Cement Height Requirements
Surface Before setting casing: Mill test/
refurbished pipe test documentation
Before drill-out: Tested under
pressure of 0.5 psi × TVD for 30
minutes
After drill-out: If set casing is
subjected to more than 360 rotating
hours integrity must be tested again
in similar manner
Sufficient cement is required to fill the annular
space between the shoe and surface
Casing must stand under pressure until
compressive strength of 500 psi w/ 72 hour
strength of 1200 psi at zone of critical cement:
 Extends from the base of the surface
casing to cover the lower 20% of the
string (minimum of 300’)
 Covers the bottom 20% of the
intermediate/ production string
(minimum of 300’) or to the top of the
highest productive zone
Intermediate/
Production
Before setting casing: Mill test/
refurbished pipe test documentation
Before drill-out: Tested under
pressure of 0.5 psi × TVD for 30
minutes
Unlikely to be subjected to 360
rotating hours
Cemented from shoe to point at least 600’ above
shoe in both cases
If any productive, potential flow or corrosive
zone: the cementing job is determined by:
 Calculation?  600’+ above zones of
interest
 Temperature survey?  250’+ above
zones of interest
 Cement evaluation log?  100’+ above
zones of interest
 At least 200’ above previous casing shoe
Injection
Wells/
Disposal Zones
Casing must be cemented across and above all
formations permitted for injection by wells
within a ¼ mile radius
Casing must be cemented above all formations
permitted for injection into productive reservoirs
(i.e. EOR projects)
In all cases, cement height is determined by:
 Calculation?  600’+ above zones of
interest
 Temperature survey?  250’+ above
zones of interest
 Cement evaluation log?  100’+ above
zones of interest
Hydraulic
Fracturing
All casing strings/tubing must have a
minimum internal yield pressure
rating of at least 1.10 times the
maximum pressure to which they
may be subjected
Pressure actuated valve/sleeves are
tested to 80% of the actuation
pressure for a minimum of 5 minutes
Minimum separation wells:
 Cement with pump and plug method to
a point at least 200’ above the shoe of
the next shallower casing string
 Cement evaluation is subject to
exemptions based on previous field
development