Reservoir Permeability Evolution in Sand Producing Wells

Transcription

1 Reservoir Permeability Evolution in Sand Producing Wells Innovative Engineering Systems Presented at 2014 Sand Management Forum Aberdeen, UK By F. Chalmers, K. Katoozi, B. Mokdad J. Tovar, O. Ibukun, S. Jimoh 5 - Presentation Template JC.pptx 1

2 Contents 2 Introduction Field and wells Sand production management programme Near wellbore deformation Permeability evolution process Conclusions so far

3 Field and wells - Chestnut 3

4 Background 4 Field information: Located in Block 22/2a of the UKCS and Operated by Centrica Energy Extended well test carried out in 2001 Two (2) producers, both completed with sand control methods (OHGP & ESS) Two (2) injectors, one completed with a sand control method (ESS), the second injector completed cased/perforated without sand control One injector failed due to lower completion failure (ESS) Sand production is as a result of a producer s lower completion failure (ESS) Total water cut has reached over 50%, wells continue to produce naturally Nauchlan Reservoir Eocene sandstone (Caran), injectite similar to Tay and Cromarty sands Undergone two (2) periods of depletion Weak but not unconsolidated Estimated 8% of matrix porosity lost in the first depletion period (EWT)

5 Sand & pore pressure management program - Performance 5 Sand and pore pressure management program implemented in 2009 Management process utilises over 40 real-time measurements for daily update and surveillance of performance 120 tonnes of sand produced, all sand produced is transported to surface Sand rates of up to 350 pptb have been recorded

6 Sand production management history 6 Date Cycle number 15/05/ st cycle 19/06/ nd cycle 10/09/ rd cycle 06/06/ th cycle 08/10/ th cycle 27/03/ th cycle 07/09/ th cycle 03/11/2011 Shutdown Cleanout 27/03/ th cycle 05/09/ th cycle 24/04/ th cycle 28/10/ th cycle

7 Near wellbore condition Nauchlan 7 Near Wellbore Deformation M odel - 16y Range (MD) : ' ' Scale : 1:162 Depth (feet) Radius of Po = inch 70 Radius of Po = inch 70 Radius of Po = inch Bit Size 70 0 Inch Caliper 70 0 inch 70 Formation Member 6960 Deformed/failed near wellbore experiments (Palmer I. 2000) 6980 Alba Near wellbore area condition is unknown Potential formation of a cavity with shear bands evolving into fractures 7000 Possible development of oriented shear bands around the wellbore 7020 Lothian Deformed/failed material at the near wellbore Nauchlan reservoir, well 16y

8 Permeability evolution - Methodology 8 Increase in productivity over time indicates a change in the petrophysical properties at the near wellbore These changes were originally considered to be caused solely by the removal of the skin. Three (3) independent routes were explored in an effort to explain the increase in production: 1. Pressure transient analysis based on BU data gathered during shutdowns and well test 2. Production history from real time pressures and flow measurements 3. Geomechanical analysis of the near wellbore area and the reservoir integrated with the two previous methods

9 Pressure transient analysis - PBU 9 WELL TEST RESULTS TEST DATE SKIN K [md] k.h REMARKS 1 20/04/ BU /05/ BU /05/ BU /08/ BU /04/ BU /06/ BU 12 Permeability increasing and skin reducing

10 Pore pressure and drawdown history 10 Reservoir pressure has been increasing due to steady and consistent water injection at ~20000 BWPD. Increase in drawdown has allowed an increase in productivity without an increase in sand production

11 Drawdown and PI Evolution 11

12 Permeability evolution 12 K has improved over time due to continuous sand production, causing a change in the geometry and mechanical condition of the near wellbore.

13 Conclusions so far 13 Production of ~120 tonnes of sand has caused a change in the petrophysical properties (permeability) at the near wellbore area. Results of this investigation indicates that evolution of permeability in sand producing reservoirs goes through at least three (3) main steps: 1. Skin reduction due to removal of pore plugging materials from the formation matrix and sand face (matrix still in a compression state) 2. Near wellbore deformation/failure due to continuous removal of material as a result of increase in the drawdown and depletion the rock framework evolves into a dilatant condition, this includes the formation of large cavities and shear bands/fractures 3. Cavities & fractures at the near wellbore area start to collapse leading to a decrease in productivity (onset of compaction) Failed ESS in well 16Y appears to be localised and the screen continues to provide support to the wellbore Way forward: Continuous production optimisation and The prevention of the near wellbore area moving into a compaction stage, which will lead to high productivity impairment

14 Sand & pore pressure management program Chestnut field 14 Thank You!