LOUD fields

 

Abstract

 

The paper defines a certain category of matured waterflood fields producing with little to no profit but still behind the recovery targets.  There are clear criteria on reservoir and production parameters of these fields.  The concept of remedial actions is discussed.

 

 

Introduction

 

Low Output Under Depleted (LOUD) fields is a category of oilfields which are struggling to reach the target recovery due to lower than expected production efficiency at late stage.

 

Below is the list of typical reasons why field development may fail to reach RF targets and get classified under a LOUD category

 

1) Gross fluid production declines faster than expected due to poor pressure support (either from aquifer or injection)

 

2) Premature water or gas breakthrough

 

3) Production cost grows faster than expected

 

Any reason above or a combination of those can lead to the vanishing profit much earlier than ultimate recovery target is achieved and hence placing the field into a LOUD category.

 

On many occasions the performance of LOUD fields can be improved by:

 

1) Establishing a strict well-by-well control of pressure/rate targets

 

2) Changing production/injection pattern

 

3) Changing vertical flow profile

 

These fields are called amendable LOUD fields and described in Appendix A.

 

 

The concept of LOUD fields redevelopment is to

 

1) Ensure production from and injection to a pay zone and no contribution from/to thief zones

 

2) Repressurize reservoir to the values above hydrostatic pressures

 

3) Set up individual (usually lower than before) pressure/rates targets to all producers/injectors

 

4) Design flow pattern to ensure a uniform sweep towards producers

 

5) Monitor rate/pressure performance and cross-well parameters and provide periodic (usually quarterly) corrections to individual rate/pressure targets

 

 

 

Redevelopment program is split into three major phases:

 

 

Phase 1  (Appendix C)

 

Complex study and designing redevelopment program – 6 months

 

 

Phase 2 (Appendix D)

 

Rebuilding facilities and changing pressure/flow pattern – 12 months

 

 

Phase 3 (Appendix E)

 

Maintaining production within multi-parameter corridor – 6 years

 

 

Many procedures require logging package described in Appendix F

 

 

Demo Model in Appendix G

 

 

 Conclusion

 

The scope, diversity and sheer volume of the study, remedial activities and monitoring efforts on enhancing the LOUD fields production is highly unusual for conventional field development business and workflow and requires a specific management, investment and technical support.

 

 

Appendix A.   Selection criteria for amendable LOUD fields

 

The table below summarizes typical parameters of those LOUD fields which can be amended with enhanced recovery methods.

 

 

 

Minimal

Nominal

Formation type

Matrix dominated sandstone or carbonates

Matrix sandstone or carbonates

Porosity

> 10 %

>15 %

Permeability

> 5 mD

> 50 mD

Oil viscosity

< 30 cP

< 10 cP

Shaliness

< 15 %

< 5 %

STOIIP

100 mln STB

500 mln STB

Drilled holes

> 20

> 100

Producing wells

> 5

> 10

Injecting wells

> 5

> 10

BSW

> 50 %

> 95 %

RF

> 80% from target

> 50 % from target

 

 

The table above silently assumes that all necessary field development data is available as per Appendix B.

 

Normally the above formations are drilled with vertical wells and by the time of getting into a LOUD stage more than 50% of wells are suspended or abandoned due to high water cut.

 

It is absolutely obvious that the presence of surface production facilities can substantially ease and accelerate the redevelopment program.

 

Particularly, the following facilities are critical to be in place:

 

1) Oil Metering Station

 

2) Water Pump Station

 

3) Desalination Plant

 

4) Pipelines towards shut-in wells

 

 

 

Appendix B.    Field Development Data

 


The table below summarizes typical data which is required for assessing the field redevelopment opportunities.

 

 

 

Minimal

Nominal

1

Field Development Plan

Yes

Yes

2

Surface facilities (maps and specs)

Yes

Yes

3

Maps and trajectories

Yes

Yes

4

Reservoir Data Logs (OH log data and deviation) 

Yes

Yes

5

Reconciled oil/gas/water production history

Yes

Yes

6

Production tests (full history tracking records)

Yes

Yes

7

Pressure history (static, bottom-hole, surveys)

Yes

Yes

8

Pressure test surveys

Yes

9

Cased-Hole production logging (PLT)

Yes

10

Cased-Hole integrity logging (CBL)

Yes

11

Drilling reports

Yes

12

Workover reports

Yes

 

 

 

 

 

Appendix C.    Complex study and designing LOUD fields redevelopment program

 

 

1) Collect and QC field data (see Appendix B)

 

2) Build geological model

 

3) Draft runs of full-field simulations in order to assess “nominal” well performance

 

4) Create discrepancy maps and analyze actual well performance against model and select candidates for calibration surveys

 

5) Massive calibration surveys campaign (CH logging and cross-well pressure interference tests)

 

6) Fine-tune the full-field simulation model

 

7) Analyze well-by-well performance and build individual pressure response model

 

8) Design waterflood pattern and set individual production/injection targets

 

9) Design surface facilities, calculate project economics and build FDP

 

10) Design Field Development Schedule (rebuilding surface facilities and well interventions)

 

 

The typical duration of the study campaign is brought in the table below:

 

Number of wells

Number of surveys

Duration

100

25

6 months

500

125

9 months

1000

250

12 months

 

 

 

Appendix D.   Rebuilding facilities and changing pressure/flow pattern

 

 

The LOUD fields redevelopment procedures can be summarized into three categories:

 

1) Rebuilding the surface infrastructure (both in injection system and production gathering system)

 

2) Workovers to recomplete well for production/injection/supply

 

3) Workovers to change vertical flow profile (injectors/producers)

 

 

Below is the list of redevelopment procedures by production/injection targets

 

 

1) Production System

 

1.1)

 

T a r g e t: Reduce the pipeline pressure in gathering stations to pre-calculated value (usually reduce below 75 psi)

 

S o l u t i o n: Install booster multiphase pumps

 

1.2)

 

T a r g e t: Ensure production from the target formation

 

S o l u t i o n:  Run logging package to evaluate the production zones and design reservoir treatments and cement jobs to shut-off production from thief zones

 

1.3)

 

T a r g e t: Ensure the maximum reservoir involvement

 

S o l u t i o n:  Run logging package to evaluate the reservoir involvement under different drawdowns and maintain drawdown target (usually below 300 psi) by manipulate gaslift/rod-pump/ESP  parameters

 

1.4)

 

T a r g e t: Repressurize the reservoir above hydrostatic pressure (usually  75 psi higher)

 

S o l u t i o n:  Temporarily limit or shut-down production from all producers, particularly high-rate water producers

 

 

 

2) Injection System

 

 

2.1)

 

T a r g e t: Reduce the pipeline pressure in injection system to pre-calculated value (usually reduce below 800 psi)

 

S o l u t i o n: Change water pumps (usually for lower pressure pumps)

 

2.2)

 

T a r g e t: Ensure injection to the target formation

 

S o l u t i o n:  Run LOUD logging package to evaluate the injection zones and design reservoir treatments and cement jobs to shut-off injection to thief zones

 

2.3)

 

T a r g e t: Ensure the maximum reservoir involvement

 

S o l u t i o n:  Run LOUD logging package to evaluate the reservoir involvement under different pressure and maintain individual pressure target (usually below 300 psi) by installing and manipulating wellhead pump or a choke

 

2.4)

 

T a r g e t: Repressurize the reservoir above hydrostatic pressure (usually 225 psi higher)

 

S o l u t i o n:  Temporarily limit or shut-down production from all producers, particularly high-rate water producers, put shut-in injectors back on stream and convert some producers into injectors.

 

 

 

Appendix E.    Maintaining production within multi-parameter corridor

 

 

Once the LOUD field is rebuilt and repressurized the future production should be confined to pre-calculated targets set up separately on pressure and rates.

 

 

Below is the list of monitoring/amending activities to be run across the field

 

1) Install permanent pressure/rate sensors

 

2) Monitor productivity and cross-well interference parameters

 

3) Correct pressure/rate targets (usually every 3 months)

 

4) Create and analyze discrepancy maps on well performance and select candidates for downhole surveys

 

5) Downhole surveys on observers and selected underperforming wells

 

6) Remedial jobs on the wells with integrity or flow profile issues

 

 

The above activities heavily utilize advanced software and methodological tools to analyze individual well performance and provide frequent fine-tuning of pressure/rates targets and identify the underperforming wells.

 

 

Appendix F.    LOUD logging package

 

LOUD program intensively uses the following well logging services:

 

1) Evaluate completion integrity

 

2) Evaluate borehole flow profile

 

3) Evaluate formation flow profile

 

4) Evaluate behind-casing communications

 

5) Evaluate formation pressure in flowing units

 

6) Evaluate formation response to varying delta pressure

 

7) Evaluate formation porosity and saturation

 

LOUD is using proprietary hardware, software and methodologies to design multi-rate logging procedures and interpret the acquired data.

 

Below is the list of memory sensors in toolstring:

 

1) NAV – Gamma Ray, 3-axis accelerometer, short sensor MID

 

2) PRESS – Borehole Fluid Pressure

 

3) HPT – Fast response high-resolution temperature

 

4) RECAP – Borehole Resistivity and Capacitance

 

5) FBS/ILS  – Full-bore and In-Line Spinner

 

6) HEX – Heat Exchange sensor

 

7) SNL  – Spectral Noise Logging

 

8) MID – long sensors Magnetic Imaging Defectoscope

 

9) CBL  – Cement Bond Logging

 

10) MINK – Pulsed Neutron SIGMA

 

Logging jobs in injector may need hoist-operated workover to prepare borehole for survey and facilitate logging procedures

 

 

Logging jobs in producers may need hoist-operated workover to prepare borehole for survey and facilitate logging procedures as well as facilities to flow the well while logging (using nitrogen pump or swab)

 

 

 

 

For more details please contact us info@loudfields.com