Pump Intake Pressures Pump Intake Pressures Pump Intake Pressures - - PowerPoint PPT Presentation

Pump Intake Pressures in Viscous Crude Pump Intake Pressures Pump Intake Pressures in Viscous Crude in Viscous Crude

Lynn Rowlan Lynn Rowlan

2006 2006 International International Sucker Rod Sucker Rod Pumping Pumping Workshop Workshop

Accurate BHP Calculation Requires: Accurate BHP Calculation Requires: Accurate BHP Calculation Requires:

Stabilized flow conditions Determination of Liquid Level Measurement of casing pressure Measurement of casing pressure

buildup rate (at Producing and Static Conditions)

Wellbore description Oil, water and annular gas densities

• Stabilized

Stabilized flow conditions flow conditions

• Determination of Liquid Level

Determination of Liquid Level

• Measurement of casing pressure

Measurement of casing pressure

• Measurement of casing pressure

Measurement of casing pressure buildup rate (at Producing and Static buildup rate (at Producing and Static Conditions) Conditions)

• Wellbore description

Wellbore description

• Oil, water and annular gas densities

Oil, water and annular gas densities

Stabilized PBHP Stabilized PBHP Stabilized PBHP

• Requires a

Requires a Constant Constant Production Rate Production Rate

• Requires a

Requires a Stabilized Stabilized Fluid Level and Casing Fluid Level and Casing Pressure Pressure

Note: Note: In a In a stabilized stabilized well, the Liquid above well, the Liquid above the pump intake is the pump intake is 100% OIL 100% OIL regardless of well regardless of well’ ’s water s water-

• oil
• il-
• ratio.

ratio.

Gas

Brine Gradient

Oil + Gas Pump

Pc Pt PBHP

FL

Gas

Brine Gradient

Oil + Gas Pump

Pc Pt PBHP

FL

Separation of Fluids

in a Stabilized Well

Separation of Fluids Separation of Fluids

in a Stabilized Well in a Stabilized Well

• The Liquid above the pump

The Liquid above the pump intake is 100% OIL. intake is 100% OIL.

• Oil gradient: 3ft = 1 psi

Oil gradient: 3ft = 1 psi? ?

• Liquid below pump intake

Liquid below pump intake contains more water than contains more water than well test water well test water-

• oil
• il-
• ratio.

ratio.

• Liquid

Liquid below pump intake below pump intake exhibits BRINE gradient. exhibits BRINE gradient.

• Brine gradient: 2 ft = 1 psi

Brine gradient: 2 ft = 1 psi

Liquid Level Above Formation Liquid Level Above Formation with Free Gas Flow from the Reservoir with Free Gas Flow from the Reservoir

1.

• 1. Gaseous

Gaseous Liquid Column exists Liquid Column exists above the Perforations. above the Perforations.

• 2. Producing BHP =
• 2. Producing BHP =

Casing Pressure + Casing Pressure + Gas Column Pressure + Gas Column Pressure + Gaseous Oil Gaseous Oil Pressure to Pump + Pressure to Pump + Gaseous Water Gaseous Water Pressure to bottom. Pressure to bottom.

Annular Gaseous Liquid Column Exists Annular Gaseous Liquid Column Exists Annular Gaseous Liquid Column Exists

• Gas is

Gas is flowing flowing from the from the casing annulus. casing annulus.

• The Casing pressure

The Casing pressure builds up builds up when the when the casing valve is closed. casing valve is closed.

Gas Liquid + Gas Perfs Pump Flowline

Pc Pt

Gaseous Liquid Column Dip Tube

When: When: When:

Gas enters through perforations and is Gas enters through perforations and is bubbling through annular liquid from bubbling through annular liquid from perforations to gas/liquid interface. perforations to gas/liquid interface.

Determination of Gaseous Liquid Column Gradient Determination of Gaseous Liquid Column Gradient

• Determined experimentally on a given

Determined experimentally on a given well. well.

• Develop experimental correlation from

Develop experimental correlation from large number of tests and apply to large number of tests and apply to measured pressure and gas flow rate. measured pressure and gas flow rate.

Reference: Reference: “ “Acoustic Producing BHP Acoustic Producing BHP” ”

• Computed from mechanistic model

Computed from mechanistic model (not accurate in most cases) (not accurate in most cases)

Liquid % from Back Pressure Test Liquid % from Back Pressure Test

Given: Given:

• Constant Production

Constant Production

• Annular Gas Rate

Annular Gas Rate

• Annular Area

Annular Area

• Fluid Properties

Fluid Properties Determine Liquid Determine Liquid Percent in Gaseous Percent in Gaseous Liquid Column Liquid Column

Gas Low PBHP Perfs Pump Flowline

Pc Pt

Gaseous Liquid Column with 10 - 15% Liquid High FL Back Pressure Valve

Basis for Experiment:

Increase Pressure => Move Liquid Level

Basis for Experiment:

Increase Pressure => Move Liquid Level

2300 ft 2300 ft Pressure increase = 220 psi Pressure increase = 220 psi Fluid Level Fluid Level Drop 2300 ft Drop 2300 ft Gradient= 220/ 2300 = Gradient= 220/ 2300 = 0.095 psi/ft 0.095 psi/ft

The Pressure at any Depth The Pressure at any Depth in in a Gaseous Liquid Column is a Gaseous Liquid Column is Independent Independent of Surface Pressure at Stabilized Conditions

• f Surface Pressure at Stabilized Conditions

Q=constant

Pressure versus Depth Traverse Pressure versus Depth Traverse in the Annulus in the Annulus

Gradient is computed from measured pressures and levels Gradient is computed from measured pressures and levels

P P1

1

P P2

2

Back Pressure Test Setup Back Pressure Test Setup

Back Pressure Test Setup Back Pressure Test Setup

Back Pressure Regulator Loop Back Pressure Regulator Loop

Automatic Annular Liquid Level and Casing Pressure Monitoring Automatic Annular Liquid Level and Casing Pressure Monitoring

Procedure for Liquid % Test Procedure for Liquid % Test Procedure for Liquid % Test

1.

• 1. Maintain Well at Normal

Maintain Well at Normal Pumping Conditions. Pumping Conditions.

2.

• 2. Obtain Liquid Level Depth

Obtain Liquid Level Depth and the Casing Pressure. and the Casing Pressure.

3.

• 3. Increase casing pressure

Increase casing pressure with back pressure with back pressure regulator and allow well to regulator and allow well to stabilize. stabilize.

4.

• 4. Obtain

Obtain NEW NEW Liquid Level Liquid Level Depth at NEW Casing Depth at NEW Casing Pressure. Pressure.

5.

• 5. Repeat Steps 3 & 4, until

Repeat Steps 3 & 4, until Liquid Level is Near Pump. Liquid Level is Near Pump.

Casing Pressure vs. Time Casing Pressure vs. Time

Liquid Level vs. Time Liquid Level vs. Time

Gaseous liquid column gradient test using back pressure valve to set casing pressure while pumping rate is kept constant. Gaseous Gaseous liquid column liquid column gradient test gradient test using back using back pressure valve pressure valve to set casing to set casing pressure while pressure while pumping rate pumping rate is kept is kept constant. constant.

Gaseous Column Height vs. Casing Pressure for 150 MCF/D in 5” & 2-7/8” Gaseous Column Height vs. Casing Pressure for 150 MCF/D in 5” & 2-7/8”

Annular Gaseous Liquid Column Effective Gradient Factor Annular Annular Gaseous Gaseous Liquid Column Liquid Column Effective Effective Gradient Gradient Factor Factor

Adjusted Liquid Level Adjusted Liquid Level

Actual Field Collected Data Points Preliminary heavy oil data

Back Pressure Test Setup Back Pressure Test Setup

Direct annular Direct annular gas flow gas flow measurement measurement was was necessary to necessary to establish establish correlation on correlation on basis of Q/A basis of Q/A and verify and verify validity of Q validity of Q determined determined from from dp/dt dp/dt

Annular Gas Flow – dP/dT Measured Annular Gas Flow – dP/dT Measured

Close Casing Valve Close Casing Valve

Casing Pressure increase as a function of time is a measure of casinghead gas flow rate Casing Pressure increase as a function of time is a measure of casinghead gas flow rate

dP dP dT dT

Gas flow into well = 45 MCF/D Gas flow out= 45 MCF/D

Time = 0 Time = 4 min.

46.2 psi 49.4 psi

PBHP = 572.8 psi

Casing Valve Closed During Test

Calculation of annular gas flow rate is based on the increase in casing pressure per unit time during the casing pressure buildup test. Using the real gas law:

P1*V1 = Z1n1RT1 at time t1 and P2*V2 = Z2n2RT2 at time t2 where in the well:

V1 = V2 = volume of annulus minus volume of liquid T1 = T2 = average temperature R = gas constant P1 =initial casing pressure P2 = pressure at end of casing buildup test n2,n1 = number of moles of gas in annulus Then solve for (n2-n1) which is the increase in gas mass during the time (t2-t1) and convert to standard cubic feet per day.

Gas Flow Calculation Gas Flow Calculation

Requirements for Accuracy Requirements for Accuracy

Test should be short (2 to 10 minutes) so

that inflow of gas and producing bottom hole pressure remain almost constant.

Measured casing pressure buildup vs.

time should be linear indicating a constant gas rate.

ID of casing, OD of tubing and well depth

data are correctly entered in well database.

Producing BHP Producing BHP

Equivalent Gas-Free Liquid Level Equivalent Gas Equivalent Gas-

• Free Liquid Level

Free Liquid Level

Gas Low PBHP Perfs Pump Flowline

Pc Pt

Gaseous Liquid Column with 10 - 15% Liquid High FL Gas Low PBHP Perfs Flowline

Pc Pt

Gas-Free Liquid Gas Free FL

“Remove” gas from annular fluid column Reference Papers: SPE 14254 and SPE 13810