Understanding Complex Well Restrictions. Access assurance for intervention operations

Transcription

1 Understanding Complex Well Restrictions

2 Know your well The risks associated with well accessibility are greatly reduced with the aid of advanced 3D modelling of multi-finger caliper data. 2

3 Contents Well accessibility: issues, risks and impact 3D accessibility modelling technique Case study from the North Sea 3

4 The issue of well access Wells operate in physically demanding environments Environment changes over time Wells may be subjected to forces outside of original design parameters e.g. salt creep, subsidence, tectonic movements, thermal shock, pressure imbalance Often results in deformation of well structure but may not result in loss of production or integrity May not see the warning sign 4

5 The effect of well access issues Producing wells Limit interventions for production optimization Elevated risk of fish in hole (often above reservoir) Work over / Abandonment Limit ability to reach and isolate reservoir Impact on pipe recovery Impact dependent on severity Requires management Risk Rig time Costs Efficiency Profitability Safety 5

6 The solution to safe navigation Attained through understanding of Hazards Risks associated and severity Acceptable limits Well access modelling Creates 3D map of well geometry Derives critical information of Well bore ovality and curvature Drift ID as a function of BHA dimensions Delivers definitive answers on which decisions can be made 6

7 Case study North Sea HPHT field 7

8 Introduction to field Field information North Sea, central UK sector Multi-national operator HPHT gas condensate field Background Maturing asset Producing 25% of peak output Suspected reserves trapped above top of perforated interval Intervention planned for March 2013 to reperforate select wells in bid to boost production 8

9 Well X The challenge Known issues Reservoir pressures have dropped significantly during production Several wells known to have deformation of liner Risk management Other wells in field re-perforated successfully Well X is a relatively new well (2009) No major issues in previous interventions Perceived low risk and severity with respect to well accessibility Proceed with perforating 9

10 Well X The plan 1. Drift run (slickline) Max OD of (fluted centraliser) Total BHA length 26ft 2. Dummy run (E-line) 30ft dummy guns and trigger Max OD 3.32 (spent gun) Total BHA length 60ft 3. Perforating run (E-line) 2x 20ft perforating guns selected 2 7/8 OD, 6 shots per foot Total BHA length 69.85ft Run 1 Drift BHA Run 2 Dummy BHA Run 3 Perf BHA 10

11 Well X The operation Execution Rig up slickline and successfully completed drift run Rig up E-line and RIH with Dummy perforating BHA Held up and became stuck 300ft shallow of TD Reach SWL of cable (4k lbs, 50% UBS) Pump 20 bbls treatment fluid and soak for 4 hours Dispensation granted to increase SWL of cable to 5k lbs (60% UBS) BHA worked free and recovered to surface Require understanding of situation Run 1 Drift BHA Run 2 Dummy BHA? Run 3 Perf BHA 11

12 Well X The operation Diagnostics Rush mobilisation of multi-finger caliper to evaluate geometry Specialist placed on 24 hour standby to analyse data and deliver answer Identified four sites of deformation above reservoir Hold-up depth confirmed as 3rd deformation event (most severe) Approximately 11ft in length Relatively large axial deflection Further intervention aborted and well returned to production 12

13 Well X Debrief Summary Operation concluded safely, but objectives not met Approximately 20 hours lost time 10 days off production Zero production gain Could have lost the well if BHA not recovered Lessons learned Drift/dummy sequence proved successful (no live guns in well) Require more robust evaluation of downhole conditions prior to job 13

14 Resolving the complex Lack of clarity with existing evaluation A 2D approximation to a 3D problem Data acquisition not an issue Require enhanced analysis High-value well intelligence Our in-house experts applied an innovative 3D model, based on multi-finger caliper data Re-processed well X data to obtain more detailed evaluation of well geometry Determine critical measurement factors and pinpoint areas of significant risk to well access 14

15 Quantitative evaluation through 3D clarity A complete 3D model of well X was created and computations performed to determine Minimum diameter vs depth Flexural strain vs depth (curvature) Ovality vs depth 15

16 Quantitative evaluation through 3D clarity A complete 3D model of well X was created and computations performed to determine Minimum diameter vs depth Flexural strain vs depth (curvature) Ovality vs depth Model enables calculation of limiting factor for well access as a function of BHA diameter BHA length A 3D solution to a 3D problem

17 Quantitative evaluation through 3D clarity Drift diameter vs tool length Provides quantitative evaluation of well access limits for given toolstring diameter Drift diameter vs BHA OD vs BHA length Shading represents safety factor in tool OD (e.g. to account for gun swelling) 17

18 The shape of things to come 3D view 1: North-South 3D view 2: East-West 18

19 Accurate answers for qualified decisions Results Model verified that drift BHA would pass all restrictions Model verified that dummy perforating BHA would fail to pass 3rd deformation event from surface Conclusions Plans to re-perforate well X on hold Time required to perform multiple perforating runs Risk outweighs reward at this time 19

20 Knowing the well inside and out Going forward Modelling commissioned for a further four wells (A, B, C and D) from same field Caliper data acquired in 2007 campaign Results show deformation events significantly less severe c.f. well X Possibility of performing 4D (time-lapse) studies on selected wells to quantify rate of change of deformation events 20

21 Thank you On behalf of READ Cased Hole I would like to give my thanks to the following: SPE ICoTA for inviting me to present to you all today The operator for allowing us to share the case study My co-authors Joseph Guyan, READ Jenni Davison, READ The audience for your attention and participation 21

22 Know your well The risks associated with well accessibility are greatly reduced with the aid of advanced 3D modelling of multi-finger caliper data. 22