Change in wettability and enhancing

recovery: application for traditional and

non-traditional fields.

Geoffrey Thyne and Teresa Nealon

1 -

Outline

• What is this technique?

• Why use this technique?

• Science and Engineering.

• Practical Aspects.

• Take Home.

Why do we care about wettability?

• In petroleum reservoirs wettability is the tendency of oil to

adhere to the rock limiting oil movement and recovery.

• Wettability is an important control on the amount of recovery.

• We try to improve wettability by adding surfactants to make

the reservoir more water-wet.

Wettability

• “Hydrocarbon-wet systems retard hydrocarbon mobility”.

• “Water-wet systems promote hydrocarbon mobility”.

• But really we want to be in the middle of the wettability range

Oil-Wet Water-Wet

SPE 157094

Just making the reservoir more water-wet

may not optimize recovery

Sweet Spot

Start here

How do we link wettability to salinity?

• Wettability is the equilibrium between water, rock and oil.

• Wettability is dependent on the balance of forces between

the oil-water and water-rock interfaces.

• Forces (pressure) between surface with a water film and

oil are composed of -

– 1 – electrostatic (attractive or repulsive),

– 2 – van der Waals (attractive),

– 3 – structural or hydration (repulsive below 3-4 nm).

Hirasaki, 1991

Why Alter Wettability by Salinity?

• No Change in Normal Operations.

• Increase in Recovery is High (5-25% OOIP).

• Increase Reserves.

• Cost is Low.

• Works in Clastics and Carbonates.

• Response is Rapid (3-9 months).

• No Surfactants ($$).

• No Environmental Impact.

Key Practical Factors

• Water source can be produced water, imported water, on-site water.

• CAPEX is water treatment equipment.

• OPEX is water treatment maintenance.

• Disposal of treatment reject.

• Recoverable Oil (in-situ saturation).

• Operational Wells (#).

Industry Work Flow

• Evaluate reservoir conditions, water and oil

chemistry and rock properties (mineralogy,

mineral habitat, architecture).

• Preliminary design.

• Laboratory tests.

• Calibrated design.

ESal™ Work Flow

• Evaluation (is my field a good candidate?) – Screening – Generate Field Score

• empirical model generates quantitative score based on field, oil, water and rock properties

• preliminary water source assessment

– Scoping – Economic Assessment of Projects • expense/profit modeling (modified Kinder-Morgan)

• multiple economic evaluations and scenarios

• Experiments and Models – Wettability Measurements

• rapid scan to find optimum chemistry

– Modeling to assess other fluid-fluid-rock interactions

– Design injection fluid chemistry for optimum wettability

• Deployment – Select water source

– Generate water treatment specifications

– Install equipment

Use lab and field data to determine empirical relationships.

Input rock, water, oil and field properties to algorithm and

calculate aggregate weighted score.

Screening for good candidates

Scoping - Economic Benefits Most expensive cost scenario and $50/BBL

Reservoir OOIP wells %OOIP Project Life CumPreTax ($)

Formation BBLS in field recovery Years millions

Nugget 3 127,744,810 19 5 9 64.27

127,744,810 10 11 257.64

127,744,810 15 12.75 476.06

Nugget 2 46,115,627 18 5 7.5 14.39

46,115,627 10 10 81.50

46,115,627 15 10.5 154.61

Almond 40,486,587 125 5 10.25 20.61

40,486,587 10 8.5 79.89

40,486,587 15 9.75 148.94

Mesaverde 2 16,025,030 59 5 8.5 7.36

16,025,030 10 11 32.24

16,025,030 15 10.5 58.28

Nugget 1 9,617,523 10 5 10 4.76

9,617,523 10 10 19.37

9,617,523 15 10 35.05

Inputs

Capex and Opex

Royalty & Taxes

Pricing

Analog Method

(KinderMorgan)

Outputs

Incremental Recovery,

IRR, Revenues, NPV’s

Cum PreTax, etc.

Lab Tests - Modified Floatation

13

Initial separation

After 24 hours

Wettability Models

• Model of aqueous, oil and surface reactions.

• Double layer models assume surfaces are coated with

water and electrostatic forces are dominant.

Take Home Message

• Wettability Alteration can be employed at all stages of

operations.

• Can be deployed during drilling (unconventional).

• Can be deployed at the start of waterflood (secondary

mode).

Take Home Message

• Can be employed at end of waterflood

(tertiary mode).

Take Home Message

Questions?