Cement Calc: Complete Technical Guide

The Cement Calc workbook is the calculation engine of the cementing engineer: the spreadsheet that carries the well data, the casing geometry, the slurry densities, the volumes and the conversions of the cementing job, and returns the numbers that the mixing plant and the pumping crew execute on location. The workbook of this article is a real and proven cement calculation tool: its sheets carry the casing data of the well (the well number, the casing sizes, the casing depths, the baffle collar depth, the open hole depth, the top of the lead and the slurry weights of the lead and the tail), the conversion tables of the industry (the barrels to the cubic feet, the meters to the feet) and the lab report sheets of the slurry design, all in the format that the cementing department of the operating company uses daily.

This article walks the reader through the complete content of the workbook: the casing calculation sheet with its worked example (the 9-5/8 inch casing at 3,701 meters with the 16.20 ppg lead slurry and the 16.50 ppg tail), the slurry density and the yield calculations, the volume conversions, the water requirement, the annular volume computations, the job design numbers and the interpretation of the lab reports. The Complete Cement Technical Package (931 files: the handbooks, the courses, the Excel tools and the presentations, $249.99 one-time, instant download through the secure PayPal payment) delivers the Cement Calc workbook together with the complete library of the cement calculation tools, and this article shows the reader how the numbers of the workbook are derived.

1. What the Cement Calc Workbook Computes

The cement calculation sheet of the industry serves one purpose: to convert the job design into the working numbers of the execution. The workbook of the package performs the complete set of the calculations that the cementing engineer needs before the pumps start:

• The casing geometry: the casing sizes, the casing weights, the depths of the casing and the open hole: the physical framework of the job: the sheet stores the 9-5/8 inch casing data, the 13.375 inch previous casing, the casing TD at 3,701 meters (12,142.39 feet) and the baffle collar depth of 3,676.6 meters (12,062.34 feet);
• The hole volumes: the volume of the open hole and the casing computed from the geometry: the sheet includes the calculation of the hole size from the hole volume derived from the logs, the classic inverse calculation of the cementing practice;
• The slurry densities: the lead and the tail slurry weights: the 16.20 ppg lead and the 16.50 ppg tail of the example: the two-density design of the deep wells, the lower-density lead filling the upper annulus and the higher-density tail covering the critical zones of the shoe;
• The slurry volumes and the yields: the volume of the slurry per sack of cement, the sacks required, the mix water and the additives per slurry: the numbers that the bulk plant reads;
• The unit conversions: the barrels to the cubic feet (the sheet converts the 59.25 barrels into the 332.68 cubic feet), the meters to the feet (the 3,701 m into the 12,142.39 ft): the conversion tables of the workbook that keep the metric and the field units in one file;
• The lab data: the confirmation and the pilot test data of the slurries: the retarder, the expansion additive, the compressive strength enhancer and the water type (the drilling water or the sea water): the link between the laboratory design and the field execution.

The workbook therefore covers the whole chain of the cement calculation: from the well geometry through the slurry design to the volumes and the conversions that the pumping program needs, and every number of the chain appears in the single file that the cementing crew carries to the location.

2. The Casing Data Sheet of the Workbook

The first sheet of the workbook is the casing calculation page, the sheet that carries the physical data of the well and the casing string. The example data of the workbook belong to the well of the MOL company with the well number KOT-1, and the sheet shows the complete set of the numbers that the cementing calculation needs:

• The casing size and the weight: the 9-5/8 inch casing with the 10.75 inch outer diameter dimension and the casing weight of the P-110 grade at 53.5 lbs/ft (60.7 lbs/ft joint weight): the size and the grade define the annular clearance and the pressure rating of the string;
• The casing TD: the depth of the casing at 3,701 meters, converted in the sheet to the 12,142.39 feet: the two unit columns of the sheet keep the metric and the field numbers side by side, the practice of the international operations;
• The baffle collar: the depth of the baffle collar at 3,676.6 meters (12,062.34 feet): the collar depth defines the top of the cement plug during the displacement and the volume of the cement that must reach the shoe area;
• The previous casing: the 13.375 inch surface casing: the annular geometry between the two casing strings determines the volume of the lead cement in the upper section of the annulus;
• The open hole data: the open hole TD at 12,142.39 feet and the top of the open hole at 6,543.64 feet: the interval of the hole that the cement must seal, the basis of the annular volume calculation;
• The top of the lead: the top of the cement in the annulus at the depth of 1,500 feet: the target of the lead slurry, set by the well design to isolate the shallow formations: the volume of the lead is the annular volume between the top of the lead and the top of the tail.

The casing sheet is the master data of the job: every other calculation of the workbook reads its numbers from this page, and the sheet format of the example (the labels on the left, the values in the middle, the units on the right) is the format that the field engineers recognize and trust.

3. The Slurry Design Sheets: The Lead and the Tail

The workbook carries the dedicated sheets for the lead and the tail slurries of the job, each with the lab header of the cementing department (the report number, the customer, the date, the job type) and the design parameters of the slurry. The example of the workbook shows the lead slurry at 16.20 ppg and the tail slurry at 16.50 ppg, with the reports PK13-Z-296 and PK13-Z-297 of the 2013-08-13 date.

• The lead slurry: the lower-density slurry (the 16.20 ppg of the example) that fills the upper annulus from the top of the lead down to the top of the tail: the lighter slurry reduces the hydrostatic pressure on the shallow formations and lowers the cost of the job because the lead is the bulk of the volume;
• The tail slurry: the higher-density slurry (the 16.50 ppg of the example) that covers the critical lower section of the annulus around the shoe: the tail carries the higher compressive strength, the better gas migration control and the superior bond quality at the zones that matter;
• The water type: the sheet distinguishes the drilling water and the sea water: the sea water changes the slurry properties (the shorter thickening time, the higher early strength) and the lab designs the slurry for the actual water of the location;
• The additives: the cement retarder for the deep and hot wells, the expansion additive to improve the bond, the compressive strength enhancer: the sheet records the additive list of the confirmation test, the test that validates the slurry before the job;
• The test types: the confirmation test versus the pilot test, the UCA (ultrasonic cement analyzer) strength development test versus the destructive compressive strength test: the sheet records the test history of the slurry design so the job engineer sees the complete qualification trail.

The two-density design of the example is the standard practice of the deep well cementing: the lead and the tail share the well but play different roles, and the workbook documents both designs in the format of the lab report, connecting the laboratory to the field.

4. The Slurry Density and the Yield Calculations

The heart of the cement calculation is the density and the yield of the slurry, and the formulas of the workbook are the standard formulas of the industry. The slurry density is the weight per unit volume of the mixed slurry, expressed in pounds per gallon (ppg) in the field system, and it results from the weights of the cement, the water and the additives divided by their total volume:

• The density formula: the density in ppg = (the weight of the cement + the weight of the water + the weight of the additives) / (the volume of the cement + the volume of the water + the volume of the additives): for the slurry with the cement at 94 lbs per sack, the water at 5.2 gallons per sack (the 41.8 percent by weight of the cement) and the density of the water at 8.33 ppg, the total weight is 94 + (5.2 × 8.33) = 137.3 lbs and the total volume is the cement volume (0.48 gallons per sack with the cement specific gravity of 3.15) plus the 5.2 gallons = 5.68 gallons, giving the density of 137.3 / 5.68 = 24.2 ppg, and the higher water ratio or the lighter extenders reduce the density toward the 16.20 and 16.50 ppg of the example;
• The yield formula: the yield of the slurry in cubic feet per sack = the total volume of the slurry in gallons per sack divided by 7.48 (the gallons per cubic foot): the 5.68 gallons per sack of the example gives the yield of 0.76 cu ft per sack: the yield is the number that converts the required annular volume into the number of the cement sacks;
• The mix water: the water per sack at the design water-cement ratio, adjusted for the additives (the retarder solution, the dispersant) and the mixing losses of the field equipment;
• The sacks required: the total volume of the slurry needed by the job divided by the yield: for the annular volume of 332.68 cu ft with the yield of 0.76 cu ft/sk, the requirement is 332.68 / 0.76 = 437.7 sacks of the cement: the bulk plant order number;
• The density verification: the mud balance check of the mixed slurry on location against the design density: the tolerance of ±0.1 ppg of the practice: the workbook provides the design value that the field check compares against.

The density and the yield are the two numbers that connect the laboratory design to the field execution, and the formulas of the workbook are exactly the formulas that the cementing engineers use: the same math in the spreadsheet replaces the manual calculation and removes the arithmetic errors of the pressure of the job day.

5. The Volume Calculations: The Barrels and the Cubic Feet

The volume section of the workbook computes the hole and the annular volumes from the geometry of the casing and the hole, and the conversion table of the sheet handles the units: the example of the workbook converts the 59.25 barrels into the 332.68 cubic feet with the standard factor of 5.6146 cubic feet per barrel, and the same conversion discipline runs through the whole file.

• The annular volume: the volume of the annulus between the casing and the hole (or between the two casing strings) = the annular capacity in barrels per foot × the length of the interval: the annular capacity of the annulus between the 9-5/8 inch casing and the 12-1/4 inch hole is computed from the two diameters with the standard capacity formula: capacity (bbl/ft) = (D_hole^2 − D_casing^2) / 1,029.4, with the diameters in inches: for the 12.25 inch hole and the 9.625 inch casing the capacity is (150.06 − 92.64) / 1,029.4 = 0.0558 bbl/ft;
• The casing capacity: the volume inside the casing = the inside diameter squared / 1,029.4 in barrels per foot: for the 9-5/8 inch casing with the inside diameter of 8.535 inches the capacity is 72.85 / 1,029.4 = 0.0708 bbl/ft: the displacement volume of the plug before the bump;
• The open hole volume: the volume of the open hole interval = the hole diameter squared / 1,029.4 × the length: the workbook includes the reverse calculation of the hole size from the hole volume of the caliper logs: the actual hole is always larger than the bit size, and the caliper-derived volume corrects the cement volumes;
• The total slurry volume: the sum of the annular volume between the top of the lead and the shoe, the shoe track volume and the float collar to the baffle volume: the lead and the tail split the annular part at the top of the tail depth;
• The displacement volume: the volume of the drilling fluid required to displace the cement to the baffle: the casing capacity from the surface to the baffle collar at the 12,062.34 feet of the example: the pump schedule of the job reads this number.

The volume calculations of the sheet are the arithmetic core of the job design: the error of one percent in the volumes becomes the under-displacement or the over-displacement of the cement at the critical shoe, and the workbook removes the arithmetic risk by the fixed formulas and the automatic conversions.

6. The Unit Conversions of the Workbook

The cementing operations of the international companies work in the two unit systems at once: the metric units of the well log and the oilfield units of the casing and the pumps, and the conversion table of the workbook keeps both systems in the same file:

• The length conversions: the meters to the feet with the factor of 3.28084: the 3,701 meters of the casing TD become the 12,142.39 feet, and the 3,676.6 meters of the baffle collar become the 12,062.34 feet, both numbers visible in the same rows of the sheet;
• The volume conversions: the barrels to the cubic feet with the factor of 5.6146: the 59.25 barrels of the example become the 332.68 cubic feet: the conversion row of the sheet shows the intermediate number so the engineer checks the conversion by eye;
• The density conversions: the pounds per gallon to the kilograms per cubic meter (1 ppg = 119.83 kg/m3): the 16.20 ppg slurry is the 1,941 kg/m3 and the 16.50 ppg slurry the 1,977 kg/m3: the metric reporting of the lab data;
• The capacity conversions: the barrels per foot to the liters per meter: the 0.0558 bbl/ft of the annular capacity is the 29.1 liters per meter, the number that the metric units of the displacement schedule use.

The conversion discipline of the workbook is the safety discipline of the industry: the mixed-unit arithmetic is the classic source of the cementing errors, and the fixed conversion cells of the sheet eliminate the manual factor mistakes on the job day.

7. The Job Design Numbers: The Pumping Program

The final output of the cement calculation workbook is the set of the job numbers that become the pumping program of the operation, and the sheet organizes them in the order of the execution:

• The cement volumes in the order of the pumping: the lead volume first, the tail volume second, the displacement volume third: the sheet lists the three with the depths that the crew watches on the stroke counter;
• The pump rates: the barrels per minute of each stage, derived from the well conditions and the slurry behavior: the lead at the higher rate (4–6 bbl/min), the tail at the reduced rate (2–4 bbl/min) to control the equivalent circulating density at the shoe;
• The pressures: the expected pump pressure at each stage: the circulating pressure plus the hydrostatic imbalance between the slurry columns and the mud column: the workbook’s pressure row gives the crew the reference of the surface pressure against the pumping;
• The top of the cement: the computed final depth of the cement top in the annulus from the pumped volumes: the confirmation that the 1,500 feet top of the lead target will be achieved with the planned volumes;
• The plug count: the displacement volume from the surface to the baffle: the crew’s number of the plug bump: the sheet computes it from the casing capacity and the baffle depth of the example: the most watched number of the job day.

The pumping program is the translation of the workbook’s calculations into the sequence of the pumps, and the same numbers appear in the job report that the cementing company files after the operation: the workbook is the design document of the job from the first volume to the plug bump.

8. The Lab Reports and the Quality Control

The workbook’s lab sheets record the quality control of the slurry design, and the format of the sheets (the report number, the customer, the date, the job test and the confirmation test data) is the format of the cementing lab of the industry. The example reports of the workbook (PK13-Z-296 for the lead and PK13-Z-297 for the tail) carry the complete test documentation of the two slurries:

• The confirmation test: the full slurry qualification performed before the job: the density check, the thickening time at the bottom hole circulating temperature, the free water, the fluid loss, the compressive strength development and the rheology: the confirmation test of the example is marked Yes, meaning the slurry was qualified for the execution;
• The pilot test: the initial screening of the additive concentrations in the lab: the example records the pilot test as No for the slurries, indicating that the design of the additive system was established earlier and the confirmation test sufficed;
• The compressive strength: the UCA and the destructive testing of the set cement: the UCA (ultrasonic cement analyzer) measures the strength development continuously from the sonic velocity of the cement, and the destructive test crushes the cubes: the strength at 8 and 24 hours is the release criterion of the casing after the job;
• The thickening time: the time from the mixing to the 100 Bc consistency at the bottom hole conditions: the job time plus the safety margin: the retarder concentration of the sheet is set to achieve the target thickening time;
• The temperature data: the BHST (bottom hole static temperature) and the BHCT (bottom hole circulating temperature) of the well: the design conditions of the slurry testing, recorded in the sheet’s header.

The lab report sheets of the workbook close the quality loop of the cementing operation: the field executes the slurry that the lab qualified, and the numbers of the execution return to the same file for the post-job review: the documentation of the job in one workbook.

9. The Example Job of the Workbook: The Numbers Together

Assemble the numbers of the example job to see the complete calculation of the workbook in one view. The well KOT-1: the 9-5/8 inch casing with the 8.535 inch inside diameter run to the 3,701 meters (12,142.39 feet), the baffle collar at the 3,676.6 meters (12,062.34 feet), the previous 13.375 inch surface casing, the open hole to the 12,142.39 feet with the top of the open hole at the 6,543.64 feet, and the top of the lead cement planned at the 1,500 feet.

Parameter	Value	Source / basis
Casing size	9-5/8 inch (10.75 in OD)	Casing data sheet
Casing TD	3,701 m = 12,142.39 ft	Casing data sheet
Baffle collar depth	3,676.6 m = 12,062.34 ft	Casing data sheet
Top of lead cement	1,500 ft	Well design
Lead slurry density	16.20 ppg (1,941 kg/m3)	Slurry design sheet
Tail slurry density	16.50 ppg (1,977 kg/m3)	Slurry design sheet
Volume converted	59.25 bbl = 332.68 cu ft	Conversion table
Casing capacity	0.0708 bbl/ft (8.535 in ID)	Volume calculation
Displacement to baffle	~854 bbl	Job design

• The lead slurry: the 16.20 ppg design filling the annulus from the 1,500 feet to the top of the tail: the volume of the lead is the annular capacity of the annulus between the 13.375 inch previous casing and the 9.625 inch casing over the upper interval plus the open hole annular capacity over the lower interval;
• The tail slurry: the 16.50 ppg design covering the critical interval around the shoe: the higher density for the better bond and the gas control at the bottom;
• The annular volume: the open hole annulus between the 9.625 inch casing and the hole: with the caliper-derived volume of the sheet returning the equivalent hole diameter, the total annular volume of the example is in the order of the 332.68 cubic feet shown by the conversion row (59.25 bbl): the volume that the lead and the tail together must fill;
• The cement quantity: the sacks of the two slurries: the tail volume divided by the tail yield plus the lead volume divided by the lead yield: the bulk plant order;
• The displacement: the casing capacity of 0.0708 bbl/ft × the 12,062.34 feet to the baffle = the 854 barrels of the displacement: the plug count of the job.

The assembled example shows the complete chain of the workbook: the geometry of the casing sheet, the densities of the slurry sheets, the volumes and the conversions of the calculation rows, and the displacement of the job design: one file, one job, all the numbers.

10. The Common Errors of the Cement Calculations and the Workbook’s Protection

The cementing literature of the industry records the classic errors of the manual cement calculation, and the workbook of the package is built to prevent exactly these errors:

• The unit mixing: the feet with the meters, the barrels with the cubic feet, the ppg with the kg/m3: the fixed conversion rows of the workbook keep every number in both units and the engineer reads the cross-check row at a glance;
• The oversize hole: the calculation from the bit size instead of the caliper size: the actual hole of the washouts is 5–15 percent larger and the cement volume must match: the workbook’s caliper-derived hole size calculation uses the log volumes;
• The top of the cement error: the annular volume computed on the assumption of the gauge hole: the wrong cement top leaves the shoe unprotected or the shallow zones unisolated: the workbook recomputes the top of the cement from the planned volumes;
• The lead-tail mix-up: the wrong volume of the lead pumped into the tail interval: the two-density design requires the precise depth of the tail top, and the workbook computes the split from the annular capacity table;
• The displacement error: the plug bumped short or the shoe left uncemented: the displacement volume of the workbook is computed from the actual casing capacity and the baffle depth, and the sheet flags the discrepancy between the planned and the available volumes.

The error protection of the workbook is the reason the cementing companies keep the calculation sheets as the standard document of the job: the fixed formulas, the visible conversions and the cross-check rows replace the hurried arithmetic of the job preparation with the checked and rechecked numbers.

11. The Cement Calc in the Plant Context: The Same Workbook Discipline

The calculation discipline of the Cement Calc workbook (the fixed formulas, the unit discipline, the documented inputs and the readable outputs) is the same discipline that the cement plant calculations demand, and the package places the workbook in the 09_TOOLS collection of the library where it sits next to the heat balance sheets, the raw mix design software, the kiln audit workbooks and the ball mill calculation files:

• The same formula transparency: the plant engineer who reads the Cement Calc workbook reads the heat balance sheet with the same eyes: the inputs in the labeled cells, the formulas in the visible rows, the results in the summary:
• The same unit discipline: the cement plant world mixes the kcal and the MJ, the tons and the short tons, the kg/m2 and the lbs/ft2: the conversion tables of the package’s workbooks apply the discipline of the Cement Calc file;
• The same auditability: the documented inputs and the dated reports of the workbook are the model of the plant’s energy and mass balance documentation, and the ISO 50001 audits of the plants look for exactly this documentation;
• The same team knowledge: the engineers of the companies that run both the drilling and the manufacturing operations (the oilfield service companies with the cement plants of their own) carry the same calculation culture across the two worlds.

The Cement Calc workbook is therefore not an isolated tool but the member of the family: the calculation files of the package share the format, the discipline and the reliability, and the engineer who masters one file reads them all.

12. Frequently Asked Questions

What does the Cement Calc workbook contain?

The workbook contains the casing calculation sheet with the well data (the casing sizes, the weights, the depths, the baffle collar, the open hole data), the slurry design sheets for the lead and the tail (the densities, the water type, the additives, the test reports), the volume and the conversion calculations (the barrels to the cubic feet, the meters to the feet) and the lab report sheets of the slurry qualification: the complete calculation set of the cementing job in the single file.

How is the slurry density of 16.20 ppg interpreted?

The 16.20 ppg (pounds per gallon) is the density of the mixed lead slurry: the total weight of the cement, the water and the additives per gallon of the slurry. The density of the lead is set below the density of the tail (16.50 ppg) to control the hydrostatic pressure of the cement column on the shallow formations while the heavier tail provides the higher strength and the better sealing at the shoe: the two-density design is the standard practice of the deep well cementing.

Why does the workbook convert the barrels to the cubic feet?

The cementing industry operates in the two volume systems: the pump and the tank volumes of the rig are quoted in the barrels, while the cement slurry yields and the sack volumes of the bulk plants are quoted in the cubic feet. The conversion row of the workbook (59.25 bbl = 332.68 cu ft with the factor 5.6146) keeps the two systems in one file and prevents the classic unit errors of the job arithmetic.

Can the Cement Calc workbook be used for the cement plant calculations?

The workbook is a well cementing tool, but its calculation discipline transfers directly: the same formula transparency, the unit conversions and the documented inputs serve the plant calculations of the heat balance, the raw mix design and the mill balances, and the package places the file in the 09_TOOLS collection where the plant engineer finds the full family of the calculation workbooks together.

What is the difference between the lead and the tail slurry?

The lead slurry is the lower-density cement that fills the upper annulus: its volume is the bulk of the job and its cost is lower per barrel. The tail slurry is the higher-density cement that covers the critical lower interval around the shoe: its strength, its fluid loss control and its bond quality are superior, and its volume is smaller. The two slurries together give the job both the economy and the integrity.

Is the original Excel workbook included in the package?

Yes: the Complete Cement Technical Package (931 files) includes the original Cement Calc workbook with the formulas intact, the lab report sheets, the conversion tables and the example data of the job: the buyer opens the file, replaces the example data with the own well data and reads the own job numbers in the format of the industry.

13. Conclusion

The Cement Calc workbook is the calculation engine of the cementing job: the casing geometry, the slurry densities, the volumes, the conversions and the lab reports come together in the single file that carries the job from the design to the plug bump. The example of the workbook (the 9-5/8 inch casing at the 3,701 meters, the 16.20 ppg lead and the 16.50 ppg tail, the 59.25 barrels converted to the 332.68 cubic feet) demonstrates the method with the real numbers, and the reader who follows the sheets of the article masters the calculation chain of the cementing operation.

The same discipline extends to the whole family of the cement calculations: the heat balance, the raw mix design, the kiln audits and the mill balances all share the format of the workbook, and the complete collection of the tools and the knowledge is part of the Complete Cement Technical Package: the 931 files, the one-time payment of $249.99, the instant download and the lifetime access. The purchase button below delivers the Cement Calc workbook, the calculation sheets and the full library of the cement engineer in one package.

This file is part of the Complete Cement Technical Package (931 files) available from cementequipment.org. Respective rights holders; library copy for the licensed single user.