Cementing Best Practice Jorge Sierra

December 6, 2016 | Author: hamora33 | Category: N/A
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Table of Contents Introduction

Engineering and Planning Job Procedures Plug Cementing

Squeeze Cementing

Contractor Requirements

Cementing Best Practices

Table of Contents

Table of Contents Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tips for Using This Document . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reminders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time-Saving Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 2 2 2

Introduction

Engineering and Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Engineering and Planning

Mud Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Drilling Fluid Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pipe Movement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pipe Centralization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Spacers and Flushes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Operational Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Job Volume Excess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Flow Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Downhole Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Centralizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Wiper Plugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Shoe Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Considerations for Liner Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Cement Design Priorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Priority No. 1—Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Priority No. 2—Pump Time (Thickening Time) . . . . . . . . . . . . . . . . . . . . . . . . 9 Priority No. 3—Mixability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Priority No. 4—Rheology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Priority No. 5—Fluid Loss Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Priority No. 6—Compressive Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Priority No. 7—Free Fluid and Settling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Cement Slurry Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Evaluation of Cementing Job Proposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Data Review and Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Review of Cement Job Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Interpretation of “Pilot” Test Results and Laboratory Reports . . . . . . . . . . . 12

Job Procedures Plug Cementing Squeeze Cementing

Job Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Cementing Best Practices

14 15 15 15 16 17 17 17 18 19 21

Contractor Requirements

Monitoring and Recording . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prejob Preparations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Design Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equipment / Materials Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wellbore Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pumping Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mixing and Pumping Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shallow Water Flow Cementing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait on Cement (WOC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ii

Table of Contents Plug Cementing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 22 22 22 23 24 25 25 26 26 27

Table of Contents Introduction

Engineering and Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plug Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Slurry Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spacers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Slurry Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mechanical Tools for Supporting Cement Plugs . . . . . . . . . . . . . . . . . . . . . Waiting On Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Job Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Squeeze Cementing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 29 29 30 30 32 32 34 34 35

Engineering and Planning

Engineering and Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slurry Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Washes and Spacers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prejob Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Job Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bradenhead Cement Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bull Head Cement Squeeze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Job Procedures

Contractor Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 37 38 39 40 40 41 42 43 45 45 48 50 53 56

Plug Cementing Squeeze Cementing

Cement Job Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Job Mobilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Job Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cementing Recommendation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reporting Responsibilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Designs for “Pilot Testing” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laboratory Testing Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . On-Location Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Bulk Blending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Load-Out for Land Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cement Loadout for Offshore Operations . . . . . . . . . . . . . . . . . . . . . . . . . . Prejob Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Job Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contractor Requirements

Cementing Best Practices

iiii

Introduction

Introduction

Promoting Best Practices is an ongoing effort throughout Unocal drilling operations. Given the wide variety of cementing operations going on throughout the Unocal drilling world, it is hoped that a collective sharing of Best Practices will help all areas obtain competent and economical cement jobs. Visit the Casing, Liner Running and Cementing Network LiveLink site to view the network’s charter, goals, and members’ names and contact information. Access the Toolbox section for engineering tools, calculation worksheets, and detailed job examples.

Job Procedures

Visit the Engineering Network LiveLink site now by clicking on this text link.

Engineering and Planning

This document is a guide for planning and executing cementing operations for worldwide operations. It is realized that, in some well situations, the preferred Best Practice may not achieve the best results. Every cement job should be designed for the wellbore characteristics and the cementing objectives desired.

Introduction

The purpose of this document is to teach and promote a “Best Practices” philosophy throughout the Unocal Global Drilling Community. Unocal spends millions of dollars each year on cementing operations. Poor planning and operational execution not only can lead to cement failure but can result in the loss of hydrocarbon recovery from the wellbore.

Table of Contents

Purpose

Plug Cementing Squeeze Cementing Contractor Requirements

Cementing Best Practices

11

Introduction

Tips for Using This Document This document is divided into seven main categories: Table of Contents Introduction Engineering and Planning

• Table of Contents • Introduction • Engineering and Planning • Job Procedures • Plug Cementing • Squeeze Cementing • Contractor Requirements “Engineering and Planning” and “Job Procedures” cover all the basics involved in planning and executing a primary cementing job. “Plug Cementing” and “Squeeze Cementing,” as the names suggest, contain information specific to these techniques.“Contractor Requirements” provides information about contractors’ responsibilities in ensuring the job is carried out as planned.

Reminders Job Procedures

In many of the sections, you will find white text in the blue column at the left of the page, topped with an orange bar. These comments are emphasized to indicate their importance in the success of the job.

Time-Saving Navigation

Table of Contents

The Table of Contents allows you to view the subtopics discussed within each major section. To navigate to a particular topic, just click on the entry.

The blue and orange tabs at the right of each page offer quick navigation to any major section of the document, including the Table of Contents, from any page in the document.

Contractor Requirements

Where Am I?

The title of the section you are viewing is always located in the upper right hand corner of the page, in the same color as its corresponding tab.

Cementing Best Practices

Squeeze Cementing

Colored Tabs

Plug Cementing

This document is easily navigated from either the Table of Contents or the color tabs located at the right side of every page.

22

Engineering and Planning

Engineering and Planning The first step in Engineering and Planning for cementing is to identify the purpose of the cementing operation. Once the purpose is clearly defined, the wellbore conditions and casing design must be evaluated to determine the cement placement, hydrostatic constraints, and volumes. The cementing contractor must be involved in this stage, as detailed in the Contractor Requirements section of this document.

Engineering and Planning

Application of the following guidelines for mud removal, cement and spacer design, in conjunction with a cementing software program, will enhance the displacement process and improve the probability of successful primary cementing. Cementing software can be used to help determine the optimum displacement parameters and safe operating equivalent circulating densities (ECD).

Introduction

Primary cement job failures are predominately due to a breakdown in the “displacement process,” which leads to channeling of the cement through the drilling fluid.

Table of Contents

The cementing contractor’s role begins with the Engineering and Planning stage, and his work will parallel that of the Drilling Engineer. For details, see the Contractor Requirements section.

Mud removal is best achieved through proper drilling fluid conditioning, pipe rotation or reciprocation, pipe centralization, and the use of properly designed spacers and flushes.

Job Procedures

Mud Removal

Drilling Fluid Conditioning

Pipe Movement

Cementing Best Practices

33

Contractor Requirements

Pipe rotation or reciprocation before and during cementing helps break up gelled, stationary pockets of drilling fluid and loosens cuttings trapped in the gelled drilling fluid. Pipe movement allows high displacement efficiency at lower pump rates because it helps to keep the drilling fluid flowing. If the pipe is poorly centralized, pipe movement can compensate by changing the flow path through the casing and allowing the slurry to circulate completely around the casing. The industry does not specify a minimum requirement for pipe movement, however it acknowledges that even a small amount of movement will enhance the displacement process.

Squeeze Cementing

The condition of the drilling fluid is one of the most important variables in achieving good displacement during a cement job. Regaining and maintaining good mobility is the key. An easily displaced drilling fluid will have low gel strengths and low fluid loss. Pockets of gelled fluid, which commonly exist following the drilling of a wellbore, make displacement difficult and must be broken apart.

Plug Cementing

The condition of the drilling fluid is one of the most important variables in achieving good displacement during a cement job.

Engineering and Planning

Table of Contents

In some instances, pipe movement is not recommended. For example, when equivalent circulating density and fracture pressure are very similar, or shallow gas or water influx is critical, moving the pipe can induce surge and swab pressures that could promote pipe sticking and surface casing-head pressure. The use of mechanical devices, such as some models of liner hangers, may also prevent casing movement. All of these factors must be considered when designing the displacement program.

Pipe Centralization Drilling fluid displacement is best achieved when annular tolerances are approximately 1.5 to 2 in. Centralization of very small annuli is very difficult, and pipe movement and displacement rates may be severely restricted. Very large annuli may require extreme displacement rates to generate enough flow energy to remove the drilling fluid and cuttings.

To improve centralization of the casing, adhere to the following guidelines:



Run a centralizer calculation program and reference well deviation surveys to determine the number of centralizers necessary to achieve the recommended standoff and their ideal placement.



For liner jobs, include centralizers in the lap area to aid in the displacement of cement all around the casing perimeter either in the primary cement job or subsequent squeeze job.



For highly deviated wells in which cuttings beds are likely, place the centralizer on the lower joints to hold the landing shoe off of the bottom of the wellbore. This design will allow cuttings to pass underneath and help eliminate any snowplowing effect.

44

Contractor Requirements

Use cementing simulator runs to determine the standoff necessary to achieve complete flow around the casing.

Squeeze Cementing

Cementing Best Practices



Plug Cementing

Good pipe standoff ensures uniform flow around the casing and helps equalize the force that the flowing spacer and cement exerts around the casing, increasing drilling fluid removal. In a deviated wellbore, standoff is even more critical to prevent a solids bed from accumulating on the low side of the annulus. The industry benchmark for standoff is approximately 70%, however the preferred standoff for a given well should be developed from computer modeling and will vary with well conditions.

Job Procedures

The industry benchmark for standoff is approximately 70%.

Engineering and Planning

Centralizing the casing by placing mechanical centralizers across the intervals to be isolated is critical for effectively displacing the drilling fluid and placing cement all around the casing. In poorly centralized casing, cement will bypass the drilling fluid by following the path of least resistance; as a result, the cement travels down the wide side of the annulus, leaving drilling fluid in the narrow side.

Introduction

Drilling fluid displacement is best achieved when annular tolerances are approximately 1.5 to 2 in.

Engineering and Planning Spacers and Flushes

Parameters governing a spacer’s effectiveness include flow rate, contact time, and fluid properties. To achieve maximum drilling fluid displacement, adhere to the following guidelines:

Engineering and Planning

Density

Set spacer density 0.5 to 1.0 ppg above the drilling fluid weight and at least 0.5 ppg less than the cement slurry density. In situations that require the difference between cement weight and drilling fluid weight to be less than 1.0 ppg, design the spacer density to be mid-way between the two densities.

Job Procedures

Provide a contact time and volume of spacer that will provide optimum amount of drilling fluid removal.

Introduction

Spacers and flushes are effective displacement aids because they separate unlike fluids such as cement and drilling fluid, and enhance the removal of gelled drilling fluid, allowing a better cement bond. Spacers can be designed to serve various needs. For example, weighted spacers can help with well control, and reactive spacers can provide increased drilling fluid-removal benefits. Compatibility of the drilling fluid/spacer as well as the compatibility of the spacer/cement slurry is of prime importance. Application of the compatibility procedures as outlined in the API SPEC RP10B, 22nd Edition, December 1997 is highly recommended.

Table of Contents

Compatibility of the drilling fluid/spacer as well as the compatibility of the spacer/cement slurry is of prime importance.

Contact Time

Provide a contact time and volume of spacer that will provide optimum amount of drilling fluid removal. Typically 8 to 10 minutes contact time or 1,000 feet of annular space are adequate. Rheology

Spacer must be fully compatible with drilling fluid and cement. Contact with drilling fluid must not result in flocculation, settling, or excessive rheology. Contact with cement must not decrease pump time. Stability

Spacer must remain stable with no excessive settling or separation. For all liner and tieback jobs, the spacer must be tested by “hot-rolling” at circulating temperature. Wettability

When an oil-based or synthetic-based drilling fluid is in the hole, the spacer must also be capable of converting the pipe and hole to a “water wet” condition.

Cementing Best Practices

55

Contractor Requirements

For all liner and tieback jobs, the spacer must be tested by “hot-rolling” at circulating temperature.

Compatibility

Squeeze Cementing

Spacer must be fully compatible with drilling fluid and cement.

Plug Cementing

Design spacer rheology that will provide turbulent flow where hole geometry allows. Turbulent flow of spacer is required on all liner jobs.

Engineering and Planning

Operational Priorities

Job Volume Excess

Introduction

Unless caliper data is available or excess volume is otherwise specified, use the recommended percentages in the following table to calculate cement slurry volume requirements across an open hole. Calculations of Volume Excess Depth (ft)

% Excess with Oil-Based Mud

0 to 4,000

100

50

4,000 to 8,000

75

25

8,000 to 10,000

50

15

10,000 to 18,000

35

15

Greater than 18,000

25

15

Engineering and Planning

% Excess with Water-Based Mud

Cementing Best Practices



Design spacer to be in turbulent flow as it rounds the shoe and passes the sections to be isolated.



Mix and pump cement as fast as density control, pumping equipment, material supply, and wellbore conditions allow.

66

Contractor Requirements

To maximize displacement, adhere to the following guidelines:

Squeeze Cementing

Cement flow is characterized by three flow rate regimes: turbulent flow, laminar flow, and plug flow. High-energy displacement rates are most effective in ensuring good displacement. Turbulent flow conditions are desirable, but are not required. When turbulent flow is not a viable option for a formation, use the highest pump rate that is feasible for the wellbore conditions. The best results are obtained when the spacer and/or cement is pumped at maximum energy, the spacer or flush is appropriately designed to remove the drilling fluid, and a good competent cement is used.

Plug Cementing

Flow Rate

Job Procedures

For cementing operations on offshore wells that use subsea housing, try to plan the well’s programs so that cement returns are not transported through the subsea housing. In such cases, the surface casing is usually cemented only to 500 ft above the conductor shoe. The presence of cement in the recesses of subsea housing can cause great difficulty in setting subsequent hangers or packoffs.

High-energy displacement rates are most effective in ensuring good displacement.

Table of Contents

Determining how the cement will be placed in the hole is as important as the design of the cement itself. This section discusses the operational factors that should be determined in planning a successful job.

Engineering and Planning •

Displace at high rates (8 bbl/min and higher) without exceeding the formation breakdown pressure.

Choose all downhole equipment for fit, operation, and proper installation.

Table of Contents

Downhole Equipment Choose all downhole equipment (float collars, shoes, guide shoes, centralizers, liner hanger systems, and wiper plugs) for fit, operation, and proper installation.

Determine which type of centralizer is best for a particular application by evaluating the centralizer’s suitability for the specific application, its ability to mitigate exposure for problems in the running of casing due to its design, and to provide centralization cost-effectively.



Select appropriate centralizer types, stop rings, and casing connections to minimize the risk of centralizers sliding and stacking-out. Bowspring-type centralizers provide an acceptable balance between cost and standoff for most standard cementing operations.



For highly deviated wellbores, evaluate the use of double bowspring or solid body centralizers to centralize the casing and to maintain or improve running force requirements. Tight clearances and holes drilled with bicenter bits may require the use of bow spring centralizer subs.

Wiper Plugs Top and bottom cement plugs are recommended for every primary cementing job, when possible. The bottom plug minimizes contamination of the cement as it is pumped. The top plug prevents contamination of the cement slurry by the displacement fluid and provides a positive indication that the cement has been displaced. Use composite body plugs that are easy to drill out with PDC bits.

Squeeze Cementing

Top and bottom cement plugs are recommended for every primary cementing job, when possible.

Plug Cementing

If centralizers are at risk of becoming smashed when running through existing liner tops or downhole components such as wellhead housings, choose a durable centralizer such as solid integral centralizer subs that can withstand these conditions.

Job Procedures



Engineering and Planning

Bowspring-type centralizers provide an acceptable balance between cost and standoff for most standard cementing operations.



Introduction

Centralizers

Contractor Requirements

Cementing Best Practices

77

Engineering and Planning Shoe Joint A shoe joint is recommended for all primary casing/liner jobs. The length of the shoe joint will vary. The absolute minimum length is one joint of pipe. If a bottom plug is not required, a minimum of two joints are required. Recommended Shoe Joint Lengths No. of Pipe Joints

> 18 5/8

Tag in

> 13 3/8

2 joints

> 9 5/8

3 joints

> 7 5/8

6 joints

Introduction

Casing Size (in.)

Table of Contents

A shoe joint is recommended for all primary casing/liner jobs.

Considerations for Liner Jobs



On all liner float shoes, verify that holes exist on the side of the float shoe, allowing circulation and preventing a hydraulic lockup in the event that the liner hanger fails and the liner lands on the bottom of the hole.



Use or design autofill float equipment that can be activated without setting the liner hanger, should a well control condition arise while going in hole.



Design liner hanger systems with a tieback sleeve length that allows the bottom of the tieback stem to be partially stung into the tieback sleeve when cementing the tieback casing. This will enhance the process of slacking off the tieback casing after the cement job has been completed. Buckling of the lower portion of the tieback casing after cementing can make it difficult to stab the tieback stem into place.



For ultradeep liners on directional wells with relatively high torque and drag, use a pressure-indicating method to verify that a liner is released from the running tool. The actual liner weight may be small in comparison to the drag forces, making it difficult to determine if the liner is actually released.

Plug Cementing

Ensure that the liner hanger set pressures are well above the circulation pressures that could be required while running the liner to prevent premature setting of the liner hanger.

Job Procedures Squeeze Cementing Contractor Requirements

Cementing Best Practices



Engineering and Planning

A liner hanger must be designed for the combined loading of the liner weight to be hung off and the mud weight differential on the slip area to avoid exceeding the elastic limit on the ID of the casing in which the slips are engaged.

88

Engineering and Planning

Cement Design Priorities

Cement slurry density must be within range to maintain well control. If hole conditions allow, cement slurry density should be a minimum of 1.0 ppg greater than drilling fluid weight and 0.5 ppg greater than the spacer weight.

Priority No. 2—Pump Time (Thickening Time) The pump time should include the estimated job time plus a safety factor. The safety factor must be based on wellbore parameters, operational objectives and limitations, and the accuracy of expected temperatures to which the cement slurry will be exposed during the cementing process as compared to the laboratory testing conditions. Keep the following in mind when specifying and evaluating thickening time: The first sack or leading edge of the cement is exposed to different temperature conditions and will require a different placement time than the last sack of cement.



Consider the total placement time for the lead slurry (mixing and pumping of lead + mixing and pumping of tail + displacement).

For surface and intermediate strings where cement placement is relatively easy and minimal WOC is the objective, allow a 1-hr safety factor.



For HPHT liner cementing where cement placement is critical, allow a minimum safety factor of 2 hours or 50% of the calculated job time, whichever is greater.

Priority No. 3—Mixability

Priority No. 4—Rheology The cement slurry must be pumpable, and the cement slurry rheological properties must allow effective placement, with a PV and YP as low as possible, but higher than that of spacer or drilling fluid.

Cementing Best Practices

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Contractor Requirements

Cement must be easy to mix at the cementing unit in order to achieve density control at a mixing rate that allows cement slurry placement within the available pump time.

Squeeze Cementing



Plug Cementing

Recommended Safety Factors

Job Procedures



Engineering and Planning

The pump time should include the estimated job time plus a safety factor.

Priority No. 1—Density

Introduction

Cement slurry density must be within range to maintain well control.

Table of Contents

A slurry design must address a broad assortment of well conditions and wellcontrol parameters. To maximize the performance of a slurry, adhere to these seven guidelines, listed in the order of importance:

Engineering and Planning Priority No. 5—Fluid Loss Control Design fluid loss control to specification. Excessive loss of fluid from the cement slurry has negative impact on other slurry properties.

Priority No. 6—Compressive Strength

Priority No. 7—Free Fluid and Settling Cement slurry must remain stable (free water within specification and no significant settling or separation) while fluid. Design and test for given hole conditions, i.e. for directional well test at appropriate angle.

Engineering and Planning

Cement Slurry Specifications Slurry Properties

Conductor and Surface Casings

Intermediate Casings and Drilling Liners

Production Deep Casings and Production Liners Liners and for Gas Control

Job Procedures

+ 1 ppg > drilling fluid density

Density

< Equivalent Circulating Density (ECD) to fracture formation Thickening Time

Job time plus at least one hour for safety factor For production casings or for gas control, the TT chart should display a right angle set (transition from 40 to 100 Bc in less than 15 minutes) < 0.5 %

0%

0%

Fluid Loss

NA

< 250

< 100

< 50

Rheol. (PV)

< 150

< 150

< 100

< 100

Rheol. (YP)

< 50

< 40

< 25

< 20

Comp. Strength WOC (hr to 500 psi)

< 12

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