No flaring well testing Injection Falloff testing Arild

No flaring well testing (Injection Fall-off testing) Arild Fosså | Expro Norway AS 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Traditional well testing • Low actual emissions, but aesthetically un-appealing • Important data for development decisions • Are there real alternatives ? ? 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Background Dynamic Well Test data is used as input data for the following; • Reservoir Model • Well performance Model, and • Pipeline and Facilities Models Key data provided are; • Pressures, • Temperatures • Flow rates • Fluid data (both PVT and large volume) 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway Well Bore Pressure transient from a Well Test

Example of conseq. from missing data K Field knowledge Reservoir evaluation Development strategy Miss understand : Poor estimate : • heterogeneity org. • K anisotropy • Reserves • Production profiles Wrong decisions for recovery mechanism (gas/water injection, gas cycling/depletion) Business Less Profits / Lose money Overestimate : Underestimate heterogeneity size Miss or not quantify extra permeability (fract. , dissolution) • sweeping efficiency • reserves • Underestimate Production profiles • Poor estimate segregation effects 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway Overestimate Facilities Underestimate : • Facilities • Profitability Lose money • Less Profits • Project abandonment

Backdrop on the Barents Sea • The big picture for the Barents Sea area is characterized as follows; – Same formal rules & reg’s as the rest of the NCS. – High focus from environmental groups – High focus on spill prevention from the authorities – High Political focus – (spills, blow-out risk, ice-edge, public opinion, etc. ) • Due to this an alternative way of testing wells could be of interest. 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

What is needed for a Well Test? • • Porosity Viscosity Flow rates Pressures From cores From Fluid Samples From Surface (normally) From Bottom Hole • In addition it is important to minimize the accumulator effect downhole inside the string – Well Bore Storage effects. The “simple” option…. . Gas test - Westhope, North Dakota, January 07 • Due to this there is great freedom in how you achieve the above. The elaborate option……. 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway Bideford Dolphin plant - 2010

Injection Fall-off testing • One of the parameters we have freedom over is the flow rate. Which is used to induce the pressure transient. • There is nothing stopping us from doing an injection period rather than a flow period to get the pressure transient going. • The equivalent to the normal pressure build -up would be a pressure Fall-off. • Gives the same type of data as a normal well test. – Except Fluid Data - obtained during open hole logging. 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway Classic Injection Fall-off test.

Injection Fall-off application • Traditionally Injection Fall-off tests have been used for; – Water zones and water-flood projects. • Measure pressure increases to accurately predict pressure rises from long-term fluid injection. – Verify that reservoir zones are «non-migration» types – i. e. no communication between reservoir zones. – Changes in permeability and skin over time. – Geothermal wells – Water disposal wells – Traditionally used for Gas Storage wells • There isn’t anything stopping a wider use. 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Injection Fall-off issues • Issues associated with Injection Fall-off testing vs. normal Well Tests – First, the character of the system changes. • Instead of single-phase flow, we are now faced with two-phase water/oil flow governed by relative permeability's – Second, injection of cold water induces temperature changes in the formation • This complicates the pressure behaviour through temperature effects on the oil and water viscosities. – Third, injection of water may result in the formation accidentally fracturing and in coupling of rock mechanics and fluid flow problems. • It is critically important for successful test interpretation to avoid accidental fracturing and to inject water at below the formation fracturing pressure. 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Mitigation #1 System character change • Issue - Introduction of two-phase fluids in the reservoir affecting the relative permeability's • Mitigation – Use theoretical «twobank» and «multi-bank» models. – handles the two-phase aspect of an Injection Fall-off test. – addresses changing saturation gradients, which has a significant impact on the pressure transients. 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway Horner plot example illustrating the effectsaturation of bankingprofile on an side view Schematic analytical plot Schematic saturation profile top view

Mitigation #2 Reservoir cooling • Issue - cold water reduces formation temperature, hence oil & water viscosities • Mitigation – Research show that for pressure transients governed by a moving thermal front, one should use fluidproperties corresponding to the cold injection fluid to analyse the results correctly. – Prior PVT data a plus for job planning – Extensive Fluid Sampling program for Wireline Formation Tests – Bulk sample issue for facilities & pipeline models not solved fully. (Limitation with method) 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway Pressure transient data for injection of 95°C water into a 250°C reservoir

Mitigation #3 Formation fracturing • Issue – Risk of accidental formation fracturing, possibly fracturing the cap rock. • Mitigation – Good control of the Fracture Gradient, plus injectivity modelling before a job. – Requires general good area knowledge. – Possibly that Injection-Fall. Example simulation of BHP for Injection Fall-off job off method is best suited for appraisal wells. Generic Pore-pressure & Frac gradient curve 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Mitigation #3. 1 Formation fracturing - vacuum • Other issue – In case a water-injection well is fractured, the wells often go on surface vacuum, where the fluid level can fall below surface, making surface pressure data monitoring impossible. • Mitigation – Normally the vacuum would stem from fracture propagation, which limits the issue. However, dealing with this complication requires bottom hole pressure recorders (memory or Surface Read-Out). 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Injection Fall-off application • It is not recommended to do Injection Fall-off tests for rank exploration wells. • However, we would recommend it as a possible Appraisal Well technique, provided the following; – Prior fluid data obtained from earlier exploration wells – Fluid properties available for reduced reservoir temperatures – Sufficient fluid sampling planned on actual well during OH logging – Porosity from earlier cores available – Core saturation experimental results available from earlier wells – Fracture gradient is well known for the target formation 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Other • To plan a successful Injection Fall-off test the following is needed; – More simulations than normal to model pressure transient responses to ensure correct job design. – A plan for bulk samples for pipeline and facility model experiments • Can you live without? • Can it be obtained from the Initial Flow period to surface tanks? – Bottom Hole gauges must be used for data gathering. • Equipment and services required are the same as for a normal DST, with the exception of Fluid Sampling. 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Has it been done before? • Source: NPD + Press release – http: //factpages. npd. no/factpages/Default. aspx? culture=no • • Well bore: Rig: Time frame: Formation: 7122/7 -4 S Klappmys Polar Pioneer November 2006 Kobbe (1911 -1927 m) 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway

Thank you! Arild Fosså | Expro Norway AS arild. fossa@exprogroup. com 2015 - SPE Workshop in Arctic Norway March 11 th – 12 th 2015 | Harstad, Norway