Wellplan Opticem Manual

Landmark WELLPLAN 455

ChapterCementing-OptiCem Analysis

Overview

Cementing can be used to optimize cementing operations and minimize the possibility of costly cementing errors.

In this section of the course, you will become familiar with all aspects of using the Cementing-OptiCem module, including:

Available analysis modes

Defining operating parameters

Defining cement fluids

Calculating centralizer placement

Defining the cement job

Defining analysis parameters

Analyzing results

10

Chapter 10: Cementing-OptiCem Analysis

456 WELLPLAN Landmark

Workflow

Activate Cementing by clicking the button.

Open the Case using the Well Explorer.

Define the wellbore. (Case > Hole Section Editor)

Define the workstring. Use the same dialog to define all workstrings (drillstrings, casings, liners, etc.) (Case > String)

Enter wellpath data. (Case > Wellpath > Editor)

Define the fluids used. You can define as many fluids as you want. (Case > Fluid Editor)

Define the pore pressure gradients. (Case > Pore Pressure)

Define the fracture gradients. (Case > Fracture Gradient)

Define the geothermal gradient. (Case > Geothermal Gradient)

Define the cement circulating system. (Case > Cement Circulating System)

Specify centralizer information. (Parameter > Centralizer Placement)

Specify cement job data including volumes, fluids used, back pressure and whether or not this is a foam job. (Parameter > Job Data)

If this is a foam job, specify the foam job data. (Parameter > Foam Data)

Specify wellbore temperatures, depths of interest and whether or not returns are taken at the sea floor. (Parameter > Additional Data)

Specify additional pressure that may be required to seat the plug and the eccentricity (standoff) to be used in the calculations. (Parameter > Analysis Data)

Analyze the results.



Introducing Cementing Analysis

What is Cementing?The Cementing module can be used to predict what occurs in the well during cementing operations. Cementing can be used to evaluate the effects of various conditions on the simulated cementing operation. You can use Cementing to calculate:

Safe pump rates Surface pressure Downhole pressures Nitrogen concentration Foam volume Downhole rheology Temperature thinning of fluids

Starting Cementing AnalysisThere are two ways to start the Cementing Module.

z Select Cementing from the Modules menu.

z Click the Cementing button.



Select desired Cementing-OptiCem Analysis mode from submenu, or from Mode drop-down list.

Choose Cementing-OptiCem Analysis from Modules menu, or by clicking the Cementing-OptiCem Module button.



Defining the Case Data

Refer to Entering Case Data on page 162 for instructions on entering data into the Case menu options. Case data specific to cementing will be covered in this chapter.

Specify the Volume Excess %The Case > Hole Section Editor is used to define the wellbore as the current workstring sees it. You can also use the Case > Hole Section Editor dialog to specify the extra percentage of annular cement volume required for an enlarged wellbore. This volume will be based on the Effective Hole Diameter field. For open hole sections, the Effective Hole Diameter is used to represent the actual size of the hole. If you specify the Effective Hole Diameter, the Volume Excess % is calculated based on Effective Hole Diameter. Similarly, if you specify the Volume Excess %, the Effective Hole Diameter will be calculated.

For example, if you are drilling an 8.5 inch hole that is 10% overgauge, enter 8.5 for Hole Diameter and 10 for Volume Excess %. The extra volume will be calculated. Do not use the Volume Excess % field to raise the cement top. Use Parameter > Job Data to raise the cement top.

Note: Specifying Volume Excess...

Be careful that you dont enlarge the wellbore in the Hole Diameter field and then again using the Volume Excess % field.

Enter the Volume Excess % and the Effective Hole Diameter is calculated.



Defining the Cement Job

Defining the Cement Job Fluids

Defining SpacersUse Case > Fluid Editor to define cement spacers by specifying the basic characteristics of the fluid.

You dont need to activate the spacer. Spacer use is specified using Parameter > Job Data.

To define a spacer, select Spacer from the Type drop-down list.



Defining Cement SlurriesUse Case > Fluid Editor to define cement slurries by specifying the basic characteristics of the fluid.

Specify the Standoff or Calculate the Centralizer PlacementUse the Parameter > Centralizer Placement dialog to calculate the spacing between multiple centralizers and/or the variable standoff between the casing and wellbore. Alternately, you can enter a manual standoff value that applies to the entire well. Before using this dialog, you should use the Centralizer catalog to specify all centralizers if you plan on using centralizers not already in the catalog. Access the Centralizer catalog using the Well Explorer. Refer to Working With Catalogs on page 110 for more information.

Centralizer placement calculations are typically performed before wellbore simulation. These calculations can also be performed

You dont need to activate the cement. Cement use is specified using Parameter > Job Data.

To define a cement, check the Cement box.



independently using the Centralizer Placement mode. Refer to the online help for more details concerning this dialog.

Defining the Cement Job Use the Parameter > Job Data dialog to define crucial job information such as tracer fluid types, rate, volume, and placement for each fluid in the cementing job. Refer to the online help for more information about this dialog.

Enter the maximum and minimum distance that can be used when calculating centralizer spacing.

You can specify a measured depth and standoff above the top of the centralized interval.

The Wellbore Fluid defaults from the active fluid indicated on the Case > Fluid Editor.



Defining Temperatures, Depths of Interest and Offshore Returns Information

The Parameter > Additional Data dialog is used to enter data for the Wellbore Simulator mode in the Cementing module (OptiCem). This dialog allows you to enter and manage offshore, zone depth, and temperature information.

Note: Mud Erodibility

Mud Erodibility as used in cementing and WELLPLANs Cementing-OptiCem refers to the ability of the wellbore fluid to be eroded away by a different fluid passing by it in the annulus of the well. The Mud Erodibility option is available only to Halliburton users. If you need this calculation performed, please contact your local Halliburton Zonal Isolation Group.



Specifying Additional Analysis ParametersThe Parameter > Analysis Data dialog provides supplemental control of several values before performing the Wellbore Simulator calculations.

Do not check this box because we are not taking returns at the sea floor.

Reservoir Zone and Fracture Zone are the same in this case.

Define the temperature profile to be used or import a temperature profile.

Temperature can be defined in several ways.If the Bottom Hole Circulating Temperature is known, you can specify it. You can calculate the API BHCT based on mud outlet temperature and BHST. You can specify a profile based on depth.You can import a temperature profile from WellCat.

To ensure proper plug seating, additional pressure may be applied to the casing immediately after the plug is landed.

If Eccentricity is turned off, then the wellbore simulator performs its calculations assuming 100% standoff. If you want the eccentricity calculations at a particular standoff, select the Entered Standoff option on the Centralizer Placement Dialog. Otherwise, it will run with an actual standoff profile.

Check Calculate Automatically for automatic calculation of step size. Usually you will want to check this box.

Erodibility is only available to Halliburton personnel. If you need this option, contact your local Zonal Isolation Group.



Analyzing ResultsResults for the Cementing analysis are presented in plots, tables and a report. All results are available using the View menu.

What is the Circulating Pressure Throughout the Cement Job?Use the View > Plot > Circ Pres and Den - Frac Zone plot to determine the circulating pressure fluid volume pumped at the fracture zone specified on Parameter > Additional Data.

The formation breakdown pressure at this depth is indicated by one of the curves on this plot. If the Automatic Rate Adjustment option was selected (on Parameter > Job Data), then a second curve indicates the safety factor. If the circulating pressure exceeds the fracture zone pressure, the fluid can fracture the formation and result in lost circulation from the wellbore.

If the circulating pressure exceeds the fracture zone pressure, reduce the pump rates or turn on the Automatic Rate Adjustment option. If reducing the pump rates does not completely solve the problem, decrease the density of one or more fluids (with foamed fluids, or by

These lines indicate when the various stages occur.

The circulating pressure during the displacement stage exceeds the fracture pressure.

Fracture pressure



increasing the nitrogen concentration), or decrease the volume of the heaviest stages.

If you prefer, you can view this information as ECD versus volume pumped.

Click the right mouse button anywhere on the plot to open the plot selection box. Highlight the plot you want displayed and click the left mouse button.

Observe the circulating density as a function of volume pumped.



Is There Free Fall?The View > Plot > Comparison of Rates In and Out plot displays the total annular return rate and corresponding pump rate versus the fluid pumped into the well. This data may be correlated with information in the Volume and Rates Calculations table in the Cementing Report. (View > Report)

Differences between the two rate curves indicates free fall without nitrogen injection. If free fall occurs and the well goes on vacuum, the rate out will initially exceed, and then fall below, the planned pumped rate.

What is the Surface Pressure?Use the View > Plot > Calculated Wellhead/Surface Pressure plot to view the pressure changes as varying density fluids are pumped at varying rates through the well. If the Surface Iron option was selected (on the Case > Cement Circulating System dialog) this graph is titled Calculated Surface Pressure. This data may be correlated with information in the Volume and Rates Calculations table on the cementing report.

The calculated wellhead pressure is lower than pump pressure because of the hydrostatic head and friction in the lines between the pump and cementing head.

Notice the rate out initially exceeds the rate in.

After initial high, rate out then falls below rate in.

Notice that cement free fall does occur because rate out initially exceeds the rate in, but then falls below the pump rate in.



A horizontal graph line along the x-axis indicates free fall. Often, as the majority of the cement moves from the casing to the annulus, the slope of this curve beings to increase. Usually, it continues to increase as the heavier cementing fluids are forced up the annular gap.

Automatically Adjusting the FlowrateBecause the circulating pressure exceeds the fracture pressure using the rates specified on the Parameter > Job Data dialog, you can allow the

Free Fall indicated when pressure is constant.



software to automatically adjust the pump rates. Click the Automatic Rate Adjustment box on the Parameter > Job Data dialog.

Click Automatic Rate Adjustment to have the rate adjusted to avoid exceeding the fracture pressure.

These rates will be adjusted.

If you allow automatic rate adjustment, you must specify a Safety Factor.



What Are the Adjusted Rates?The View > Plot > Comparison of Rates In and Out plot displays the total annular return rate and corresponding pump rate versus the fluid pumped into the well. This data may be correlated with information in

Using automatic rate adjustment, the maximum circulating pressure is less than the fracture pressure. Notice the safe pressure (based on safety factor) is indicated on the plot.



the Volume and Rates Calculations table in the Cementing Report. (View > Report)

Using Foamed CementUsing foamed cement is another means to reduce the circulating pressures.

The Parameter > Foam Data dialog is available only if you check the Use Foam Schedule box on the Parameter > Job Data dialog while using the Wellbore Simulator analysis mode. This dialog lets you

You can view the adjusted ratesusing this plot. Rates have beendecreased to reduce the circulatingpressure as a result of checking theAutomatic Rate Adjustment box onthe Parameter > Job Data dialog.Refer to the Job Data dialog to viewthe rates specified prior to the rateadjustment.



describe calculation methods and stages when simulating foam in a cement job.

Using the Foam ScheduleUse View > Foam Schedule dialog to calculate and view the Foam Pumping Schedule. This dialog lists liquid volume and gas rates of the fluids left in the annulus at the end of the simulation. The calculated hydrostatic pressure for the frac zone and reservoir zones are displayed at the bottom of the table. The frac zone and reservoir zones are specified using the Parameter > Additional Data dialog.

Select Constant or Staged Gas Flow to keep the nitrogen constant for a segment.The foam density will follow the pressure gradient, and thus decreases from the bottom to the top of the segment. The longer the segment, the greater the density variance.

Select this option if the nitrogen ratio will be adjusted to offset pressure changes and thus hold density more constant. Use this option only with automated nitrogen pumping equipment.

Type concentrations for Surfactant, Stabilizer.

Click the stage you want to define using the bottom portion of this dialog.

This information is read-only. It is defaulted from the Job Data dialog.

In order to foam a segment, you must check the Foam box.

The Gas Rate Stage Number is used to tell how many different gas rates are to be used under the Stage Gas option and where each of the rates are used.

Enter Quality (the volume percentage of gas in the foam) and Foam Density is calculated.

Enter Foam Density and Quality (the volume percentage of gas in the foam) is calculated.

or



Notice that some of these fluids may not be foamed. Some fluids may not appear in this report if they were pumped completely out of the annulus.

If an error occurs during the calculation process, an error dialog appears displaying a description of the error. When you finish reading it, click OK. The Error dialog and the Calculate dialog close so you can begin working on solving the source of the error.

To check results of the foam schedule calculation:1) Check the Fluid Animations Schematic to see whether the

desired top of cement was achieved, check the Final Positions of Stages table in the reports, or downhole density plot.

2) Check the circulation Pressure and Density-Fracture Zone graph and the Circulation Pressure and Density-Reservoir Zone graphs to see if the density is acceptable.

3) Adjust, rerun, and recheck the job as follows:

Click Calculate to ensure you are looking at accurate results.

Adjusted Liquid Volume and Adjusted Gas Rate sliders adjust the cement tops or placement.

These are design depths (as specified on the Job Data dialog) and may not be the actual depths. Review the View > Final Density and Hydrostatic plot for accurate cement locations.

These are the calculated hydrostatic pressure gradients for the depths of interest specified on the Additional Data dialog.

Final Gas Rate and Adjusted Final Gas Rate do not apply when you are using constant or stage gas flow.



Checking ResultsIf TOC is.... and ECD is.... then do this:Low Light 1. Increase density or decrease

quality.

2. Rerun the Foam Schedule.

3. Use the slider bar (top of Foam Data dialog) to increase the Adjusted Liquid Volume.

4. Click the Calculate button.

5. Check the Fluid Animation Schematic and the Circ Pres and Den plots.

Low Acceptable 1. Use the slider bar (top of Foam Data dialog) to increase the Adjusted Liquid Volume.

2. Repeat steps 4 and 5 above.Low Heavy 1. Use the slider bar (top of

Foam Data dialog) to increase the Adjusted Gas Rate.

2. Repeat steps 4 and 5 above.Low Light 1. Increase the density or

decrease quality.


3. Repeat steps 4 and 5 above.Acceptable Acceptable Do nothing.

Acceptable Heavy 1. Decrease density or increase quality.


3. Repeat steps 4 and 5 above.Acceptable Heavy 1. Decrease density or increase

quality.

2. Rerun the Foam Simulator.

3. Repeat steps 4 and 5 above.



* To estimate the percentage by which to change the volume, use the percentage by which the simulated foamed length differs from the desired length. (If the foamed length 1,500 feet and the desired length is 2,000 feet, increase by 33%.)

** This scenario is unlikely because the Fluid Placement calculations should prevent excessive top of cement.

Repeat these steps until you are satisfied with the results. Round the slurry and gas rate quantities before running the Wellbore Simulator.

High** Light 1. Manually decrease N2 in the Adjusted Start Gas Rate column.

2. If calculation method is constant density, also manually decrease N2 in the Adj. Final Gas Rate column.

3. Repeat steps 4 and 5 above.High** Acceptable 1. Manually decrease liquid

volume in the Adj. Liq. Vol. column.*

2. Repeat steps 4 and 5 above.High** Heavy 1. Decrease density or increase

quality.

2. Rerun the Foam Simulator.

3. Repeat steps 4 and 5 above.

Checking Results (Continued)

Wellplan Opticem Manual

Documents

Transcript of Wellplan Opticem Manual