Well Drilling (C-57) · Lesson 3 of 6

Annular Seal Mixes: Ratios, Additives, and Set Times

"Annular Seal Mixes: Ratios, Additives, and Set Times" is lesson 3 of 6 in the Well Drilling (C-57) Learning Hub. It opens with "What Is Allowed in a Seal" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. What Is Allowed in a Seal
  2. Neat Cement and Sand Cement Ratios
  3. Concrete and Additive Limits
  4. Bentonite Seals
  5. Set Time and Heat

The worked example in the course applies this lesson to a realistic job in 7 steps.

What you'll be able to do

  • Explain the main idea of "Annular Seal Mixes: Ratios, Additives, and Set Times" in plain language you can use on the exam.
  • Apply this step with confidence: "Concrete and Additive Limits".
  • Apply this step with confidence: "Bentonite Seals".
  • Apply this step with confidence: "Set Time and Heat".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Annular Seal Mixes: Ratios and LimitsBoreholeCasing2 in radial thickness of sealmax 0.4 in = 1/5 of 2 in3/8 inpasses1/2 intoo bigMinimum set time before work resumesType I / II24 hoursType III12 hoursType V6 hoursWORKED EXAMPLE: 20 SACKS, TYPE IICement: 20 x 94 lb = 1,880 lbNeat-cement water: 20 x (5 to 6) = 100 to 120 galBentonite max: 1,880 x 6% = 112.8 lbSand-cement: sand max 20 x 188 = 3,760 lb, water 20 x 7 = 140 galAggregate max: 2 in x 1/5 = 0.4 in 3/8 in (0.375) passes; 1/2 in failsBentonite 200 lb: 1 gal per 2 lb = 100 gal of waterPoured 6:00 am: Type II resumes 6:00 am next day20 sacks neat: 100-120 gal water, bentonite no more than 112.8 lbAggregate no larger than 0.4 in in a 2-in seal; wait 24 h (Type II)Source: DWR Well Standards (Bulletin 74-90/74-81), Part II, Sec. 9.D (sealing material) and 9.E (radial thickness)CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: What Is Allowed in a Seal

Section 9.D of the DWR Well Standards (Bulletin 74-81 as supplemented by Bulletin 74-90, Part II) says sealing material shall consist of neat cement, sand cement, concrete, or bentonite. Cuttings from drilling, or drilling mud, shall not be used for any part of the sealing material. Mixing water should generally be drinking-water quality, compatible with the material, and free of petroleum products and suspended matter; in some cases non-potable water with a maximum of 2,000 mg/L chloride and 1,500 mg/L sulfate can be used for cement-based mixes. Cement must meet ASTM C150 as cited by the standard.

Step 2: Neat Cement and Sand Cement Ratios

Neat cement made with Type I or Type II Portland cement is one 94-lb sack of cement mixed with 5 to 6 gal of clean water. Sand cement is not more than 188 lb of sand per 94-lb sack (2 parts sand to 1 part cement by weight) with about 7 gal of clean water, which the standard calls a '10.3 sack mix'. Use less water if you use less sand, and more water if bentonite, accelerators, or retardants are added. Any variation from these ratios must be approved by the enforcing agency, and the mix must be mixed thoroughly so no lumps remain.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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