Permian Basin Disposal Well Review

Background

Commission staff have determined that for applications to dispose of oil and gas waste into both productive and non-productive formations within Districts 7C, 8A, and 08, additional information is required for the Commission to find that (1) the use or installation of the injection well is in the public interest; (2) the use or installation of the injection well will not endanger or injure any oil, gas, or other mineral formation; and (3) with proper safeguards, both ground and surface fresh water can be adequately protected from pollution. Rules 9(3)(C) and 46(b)(1)(D) state,

The commission may require an applicant for a disposal well permit under this section to provide the commission with additional information such as logs, geologic cross-sections, pressure front boundary calculations, and/or structure maps, to demonstrate that fluids will be confined if the well is to be located in an area where conditions exist that may increase the risk that fluids will not be confined to the injection interval. Such conditions may include, but are not limited to, complex geology, proximity of the basement rock to the injection interval, transmissive faults, and/or a history of seismic events in the area as demonstrated by information available from the USGS.

Applicability

All disposal well applications in Districts 7C, 8A, and 08 will undergo a Permian Basin Disposal Well Review. Injection wells that are not for oil and gas waste disposal, for example, injections wells for waterflood, other enhanced recovery, pressure maintenance, or storage are not part of this review.

Application Information

The checklist below outlines the information required for disposal well applications that undergo a Permian Basin Disposal Well Review. Applicants are required to submit the underlying source documents for all parameters provided in the review. Applicants are encouraged to submit any additional information that will assist with the review.

The technical review will, in part, focus on the applicant’s thorough characterization of the in-situ stresses of the confining zones (i.e., upper and lower confinement) and the permitted injection interval, as well as the average reservoir pressure in the permitted injection interval.

The Permian Basin Disposal Well Review application submittal will consist of the Excel Workbook, provided by RRC, which includes three (3) spreadsheets (Well Template, AOR Template, and MSIP & MDIV). All supporting references (e.g., step rate test data, pressure test results, etc.) and explanation (reports, analysis) must be included.

Checklist:

• Completed UIC Permian Pressure Review V1.0 Workbook:
  • ‘Well Template’ Worksheet
    • Columns C and D are user inputs of parameters useful to the review and page references to the appended source documents.
  • ‘AOR Template’ Worksheet
    • Columns A-AD completed for ½-mile AOR
    • Columns A-Q completed for 2-mile AOR
    • If any information is unavailable or not applicable do not estimate, mark clearly as “unavailable” or “NA.”
• Map: 2-mile AOR, showing all offset wells including index numbers corresponding to AOR Template (index numbers will increase with distance from the subject well). If faults are known to the applicant, include them on the map and the cross section. If the RRC has publicly available evidence of faulting in the AOR, it may be considered in the review.
• 2-Mile+ Cross Section: Must be representative of the 2-mile AOR. Include any well from which reference data was obtained.
• ‘Well Template’ Worksheet Data Appendix and/or Report: Include source documents for referenced data such as step rate tests, well logs, bottomhole pressure tests and the associated analysis.
• ‘AOR Template’ Worksheet Data Appendix and/or Report: Include source documents for plugging, cementing and relevant completion information for all wells within 1/2-mile. Information may be submitted to preemptively supplement incomplete RRC records found within 2 miles of the subject well.
• Professional Engineer or Geologist Seal – The application, as a whole, or specific engineering or geologic work products such as AOR, pore pressure analysis, and fracture gradients must be signed and sealed by a Texas-Licensed Professional Engineer or Geologist as applicable.

COMPONENTS OF 'WELL TEMPLATE' TAB DISCUSSION

CONFINEMENT

In-Situ Stress Data and Analysis -

RRC will accept the values for the hydraulic fracturing pressures (e.g., least principal stress, frac gradient) from injection testing and analysis, as well as geophysical well log derived values (e.g., sonic logs).

A Step Rate Test (SRT) is the preferred option for determining injection pressures as a function of injection rate, and that same test can be used to determine the least principal stress for a properly isolated interval (i.e. frac gradient). Guidelines for SRT test designs can be found on the RRC website (Step Rate Test (SRT) Guidelines). Additionally, fracturing pressures may be obtained by Extended Leak Off Tests (XLOT), Diagnostic Fracture Injection Test (DFIT) or another industry standard testing.

Additionally, in-situ stress (i.e., frac gradient) can be approximated from a di-pole sonic or full waveform sonic log. Industry trade names for the sonic logs will vary.

The analysis of this data needs to be provided under signature from a Professional Engineer/Geologist (P.E./P.G.), including a digital copy of the data in an EXCEL format. If stress estimates from sonic logs are used, the data set should include the density (rock) gradient, pore pressure gradient, and formulas used to calculate Poisson’s Ratio and least principal stress (e.g., frac. gradient) included in the submittal.

RRC will accept these geomechanical properties by reference to data from offset wells. The applicant needs to indicate the relevance of the offset well being used by including a properly annotated cross section that is inclusive of that reference well. This will require the applicant to expand the span of the cross section required to define the 2-mile AOR, to a distance that includes the reference well.  In addition, the applicant should have a PE/PG analyze the source data used in the same manner as they would if that source data were the applicant’s own well data.

PORE PRESSURE

Pore pressure, in the context of the Permian Basin Disposal Well Review, will be synonymous with estimated or measured, initial average reservoir pressure.  Pore pressure will in almost all applications, apart from permit amendments, be referenced to measurements made in offset wells, or estimates made using offset well data.  The applicant will provide documentation explaining the characteristics of the references as well as an explanation of how the measurement or analysis of the pore pressure was made and verified. The reference well should be included in the cross section. If the reference well is further than the 2-miles required to be included in the representative cross-section, the cross-section must be extended to include the reference well to demonstrate that it is applicable and stratigraphically correlative.

PERMIT INTERVAL

If the application requests an MSIP that will fracture the formation, the permitted interval shall be reviewed so the upper and lower boundaries of the permitted injection interval are mechanically competent to prevent fracture growth out the injection interval. Under no case is fluid allowed to escape the permitted injection interval, even if it may be part of a larger geological body. Confining intervals, above or below, must have a minimum 25 ft of thickness in addition to adequate mechanical properties to be considered confining.

DATA APPENDIX AND REPORT

• Well logs may be submitted digitally as LAS or image files with the formation contact picks annotated. These may be submitted as separate files and clearly identified.
• Large graphic images, such as cross-sections, may be submitted as separate files and clearly identified.
• Most of the Supplemental Report documents and reference materials should be collated into a single .pdf file with a table of contents and page numbers.

COMPONENTS OF 'AOR TEMPLATE' TAB DISCUSSION

All wells within the 2-mile AOR should be identified and listed in order of distance (nearest to furthest) from the proposed disposal well. It is the Applicant’s responsibility to accurately report all wells for which it has actual knowledge and to perform a due-diligence search within the AOR for those wells using available archives. The technical review of the 2-mile AOR will be comprised of two categories: ½-mile and 2-mile:

• The ½-mile review will focus on zonal isolation via wellbore penetrations. For all penetrating wells in the ½-mile radius, casing and cementing information are required to assist the Commission in determining that fluids will not escape the injection interval. Competent cement is required across the injection interval in all wells within ½ mile from the proposed disposal well. All inactive wells require annular cement, and wellbore plugs to prevent fluids from reaching the Base of Usable Quality Water (BUQW). Wells without proper documentation are considered ‘not compliant’ with the isolation requirements of this ½-mile portion of the AOR. The AOR Data Appendix should include labelled or numbered plugging and cementing records for all wells within ½-mile radius. For the purpose of this review, the proposed well’s Base of Usable Quality Water (BUQW) depth, determined by the Geological Advisory Unit’s (GAU) Groundwater Protection Determination (Form GW-2) should be projected horizontally across the AOR to offset wells. For example, if the BUQW determination has deepened since the time of drilling for an offset well in the AOR, the modern, deeper BUQW depth is the assumed protection depth.
• The 2-mile AOR will focus on unknown (i.e., no well data available) or orphaned wells. If present, these wells will result in a deduction of the permit’s MSIP but will not necessarily be cause for denial of the application, unless conditions exist which the Commission cannot find injectate will be confined to the permitted interval. (The 2-mile wellbore information that is available will be part of the permit record and will be used should a confinement issue occur within the AOR.)

'MSIP and MDIV' TAB DISCUSSION

This is the MSIP & MDIV determination of the Permian Basin Disposal Well Review. If the ½-mile AOR has concluded that zonal isolation exists. MSIP will be determined by an assessment of the least principal stresses (e.g., frac gradients) of the stated confining intervals and the injection interval.

MAXIMUM SURFACE INJECTION PRESSURE (MSIP) METHODOLOGY

The MSIP gradient (psi/ft) is determined by using the least of the differences of the upper and lower closure pressure minus the hydraulic pressure (psi) divided by the upper confinement depth (ft).

If unknown wells, unplugged and inactive wells, or orphaned wells exist in the 2-mile AOR (but outside the 1/2-mile AOR) and are not remedied, then a 0.05 psi/ft penalty is deducted from the output of the MSIP gradient calculation.  

If the Applicant requests a gradient lower than the output of this review, the permit will reflect the applicant’s request. No MSIP gradients greater than 0.50 psi/ft will be granted administratively. 

MAXIMUM DAILY INJECTION VOLUME (MDIV) METHODOLOGY

Maximum daily injection volume is determined by scoring the initial average reservoir pressure of the proposed location. Acceptable methods for determining this value are found above in 'COMPONENTS OF 'WELL TEMPLATE' TAB - Discussion– Pore Pressure.' The scores and MDIV outputs are as follows:

MAXIMUM INJECTION RATE (MIR) METHODOLOGY

The MDIV is not only a standard permit condition that limits volume on a daily basis in barrels per day (bbl/day), but also functions as an instantaneous rate limit. MDIV divided by 1,440 minutes/day will result in an MIR in barrels/per minute (bbl/min.) that must not be exceeded.

PERMIT SPECIAL CONDITIONS

Permits granted after a complete Permian Basin Disposal Well Review will be subject to (but are not limited to) the following special permit conditions:

• Bottomhole pressure measurements – Initial and Periodic (annual occurrence, includes instantaneous shut-in pressure measurement, ISIP) reported to TexNet Injection & Pressure Reporting Tool (https://injection.texnet.beg.utexas.edu/) as well as reports submitted to UIC.
• Daily injection volumes / surface injection pressures – reported monthly to TexNet Injection & Pressure Reporting Tool (https://injection.texnet.beg.utexas.edu/).
• Fracture gradient – one-time occurrence, prior to injection, obtained through step rate test or log-derived.
• Cement Bond Log (CBL) – on long string casing.
• Well log – includes at a minimum, gamma ray, resistivity, porosity, and full-waveform acoustic tracks.
• Maximum Instantaneous Rate (MIR) – The Maximum Daily Injection Volume will serve as an instantaneous rate limit [MDIV (bbl/day) / (1440 min./day) = MIR].

Seismicity

Applications within 9.08 km to 25 km of historical seismic events will undergo a seismic review. Generally, staff will perform the Permian Basin Disposal Well Review and, if the well is shallow, that review will determine the permit outcome and permit conditions. However, the State Seismologist may identify areas which seismicity is a concern and the applications in such an area will be subject to seismic guidelines. In areas of seismic concern, the permit conditions will be determined according to seismic guidelines. Details of the Seismic Review may be found here.  

User Guide: Permian Basin Disposal Well Review Spreadsheet

This portion of the document provides specific instructions for completing the ‘WELL TEMPLATE’ Tab. Users should enter their values in column ‘C’ of the spreadsheet, corresponding to the predefined variable titles in column ‘A’. The information captured in this template is essential for regulatory tracking and the evaluation of the permit application. Below is a description of each variable to help users source and enter the correct data. In column ‘D’ the applicant should reference page numbers, from the source documents and supplemental report, highlighting the source of the data entered into column ‘C’.  For example, the proposed depths to the boundaries of the confining and injection zones will likely be interpreted from nearby well logs, and fracture gradients will be based on nearby step-rate or other well tests. The supporting documentation must be submitted with the application. Relevance of data from an offset well should be discussed in the Supplemental Report, illustrated on the cross-section, and referred to in column ‘D’ of the ‘Well Template’ tab.

The Commission recommends the reference information be submitted as a Supplemental Report as follows:

How to Use the EXCEL file Template

1. Open the EXCEL File – Save the file with an Operator and Lease name and well number associated with the application (for example, “GulfCo_Spindletop_1.xlsx”).  Navigate to the designated tab containing the data entry form.
2. Identify the Required Fields – Each row in Column A represents a specific data point.
3. Enter Your Values – Input the relevant data in Column C based on the descriptions provided.
4. Ensure Accuracy – Use the correct formatting for numbers, coordinates, and other measurements.  This includes the acceptable value range, which is checked for each cell entry using EXCEL’s data validation function. All depths should be entered as True Vertical Depth (TVD).
5. Source of Data – Add the location of the data source found in the Supplemental Report, to column ‘D’ in the ‘WELL TEMPLATE’ tab.
6. Save and Submit – Save the completed file and follow submission guidelines.

Variable Descriptions in 'WELL TEMPLATE' TAB