AU2002324824A1 - Lost circulation materials (LCM's) effective to maintain emulsion stability of drilling fluids - Google Patents

Description

TITLE: LOST CIRCULATION MATERIALS (LCM's)

EFFECTIVE TO MAINTAIN EMULSION STABILITY OF DRILLING FLUIDS

Field of the Invention

The present invention relates to lost circulation materials, and to methods for maintaining emulsion stability in emulsion type drilling, drill-in, and completion fluids (hereinafter sometimes collectively referred to as "drilling fluids") containing lost circulation material(s). Background of the Invention Drilling fluids serve various functions, such as promoting borehole stability, removing drilled cuttings from the wellbore, cooling and lubricating the bit and the drillstring, as well as controlling subsurface pressure. Certain subsurface conditions can cause, or lead to, "loss of circulation," or the loss of whole drilling fluid in quantity to the formation. Examples of such subsurface conditions include, but are not necessarily limited to: (1) natural or intrinsic fractures, (2) induced or created fractures; (3) cavernous formations (crevices and channels), and (4) unconsolidated or highly permeable formations (loose gravels).

Lost circulation materials are used to minimize loss of circulation. The lost circulation material forms a filter cake that effectively blocks voids in the formation. Currently, lost circulation materials include fibrous materials, such as cedar bark and shredded cane stalk, flaky materials such as mica flakes, and granular materials such as ground limestone, wood, nut hulls, corncobs, and cotton hulls. Unfortunately, low electrical stability values have been reported for invert emulsion drilling fluids containing fibrous cellulosic lost circulation material If the electrical stability value of a drilling fluid becomes too low, water wetting of solids occurs, which may cause the rheological properties of the fluid to break down, rendering the drilling fluid ineffective and even resulting in a shutdown of drilling operations

Lost circulation materials and methods of use are needed which maintain electrical stability, and thereby emulsion stability of drilling fluids Summary of the Invention

The invention provides a method for maintaining electrical stability in a drilling, drill-in, or completion fluid comprising lost circulation material (LCM), said method comprising providing an initial fluid selected from the group consisting of a drilling, drill- in, or completion fluid, said initial fluid having effective rheology and fluid loss control properties, adding to said initial fluid a fibrous LCM consisting essentially of a quantity of high lignin lost circulation material (HLLCM), thereby producing a treated fluid In another aspect, the invention provides a method for maintaining electrical stability in a drilling, drill-in, or completion fluid, said method comprising providing an initial fluid selected from the group consisting of a drilling, drill- in, or completion fluid having effective rheology and fluid loss control properties, and using as LCM in said initial fluid a fibrous HLLCM having a water retention value of about 1 or less. In yet another aspect, the invention provides a method for maintaining electrical stability in a drilling, drill-in, or completion fluid, said method comprising: providing an initial fluid selected from the group consisting of a drilling, drill- in, or completion fluid, said initial fluid having effective rheology and fluid loss control properties; and using grape pumice as a lost circulation material.

In preferred embodiments, said initial fluid exhibits a first electrical stability value and said treated fluid exhibits a second electrical stability value that is a maximum of 18% less than said first electrical stability value; more preferably 15% less than said first electrical stability value; most preferably 12% less than said first electrical stability value. The initial fluid preferably is an emulsion base fluid, most preferably an invert emulsion fluid. The fibrous HLLCM preferably has a water retention value of about 1 or less, more preferably about 0.5 or less, even more preferably about 0.3 or less. Preferred HLLCM' s are selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from processing plant material into paper. A most preferred HLLCM is grape pumice. The HLLCM preferably comprises a particle size distribution of from about 10 μm to about 200 μm.

In another aspect, the invention provides a fluid selected from the group consisting of a drilling, drill-in, or completion fluid having effective rheology and fluid loss control properties and comprising a lost circulation material consisting essentially of an HLLCM. In another aspect, the invention provides a fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having- effective rheology and fluid loss control properties and consisting essentially of an LCM having a water retention value of about 1 or less. In another aspect, the invention provides a fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having effective rheology and fluid loss control properties and comprising a fibrous LCM, said fibrous LCM consisting essentially of materials selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from the processing of plant material into paper.

In yet another aspect, the invention provides a fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having effective rheology and fluid loss control properties and comprising a fibrous LCM consisting essentially of grape pumice. In preferred embodiments, the initial fluid exhibits a first electrical stability value and a fluid comprising said HLLCM exhibits a second electrical stability value that is a maximum of 18% less than said first electrical stability value; more preferably 15% less than said first electrical stability value; most preferably 12% less than said first electrical stability value. The initial fluid preferably is an emulsion base fluid, most preferably an invert emulsion fluid. The fibrous HLLCM preferably has a water retention value of about 1 or less, more preferably about 0.5 or less, even more preferably about 0.3 or less. Preferred HLLCM' s are selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from processing plant material into paper. A most preferred HLLCM is grape pumice. The HLLCM preferably comprises a particle size distribution of from about 10 μm to about 200 μm

In yet another aspect, the invention provides a spotting pill comprising from about 1 to about 100 ppb of an HLLCM and a carrier liquid Preferably, the spotting pill comprises from about 5 to about 50 ppb of an HLLCM and a carrier liquid

The HLLCM preferably consists essentially of materials selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from the processing of plant material into paper In a most preferred embodiment, the HLLCM is grape pumice In yet another aspect, the invention provides a spotting pill comprising from about 1 to about 100 ppb grape pumice a carrier liquid, preferably from about 5 to about 50 ppb of grape pumice and a carrier liquid

The carrier liquid preferably is selected from the group consisting of a polyalkylene oxides and copolymers thereof, polyalkyleneoxide glycol ethers, glycols, polyglycols, tripropylene glycol bottoms, and combinations thereof In a preferred embodiment, the carrier liquid is selected from the group consisting of ethylene glycols, diethylene glycols, triethylene glycols, tetraethylene glycols, propylene glycols, dipropylene glycols, tripropylene glycols, tetrapropylene glycols, polyethylene oxides, polypropylene oxides, copolymers of polyethylene oxides and polypropylene oxides, polyethylene glycol ethers, polypropylene glycol ethers, polyethylene oxide glycol ethers, polypropylene oxide glycol ethers, and polyethylene oxide/polypropylene oxide glycol ethers In another preferred embodiment, the carrier liquid is selected from the group consisting of ethylene glycol, tripropylene glycol bottoms, and combinations thereof In a most preferred embodiment, the carrier liquid comprises tripropylene glycol bottoms. In a most preferred embodiment, the HLLCM is grape pumice, most preferably combined with tripropylene glycol bottoms. Where alkalinity of the drilling fluid is a concern, the pH may be maintained by using about 0.2 lb soda ash to about 1 lb grape pumice, in the spotting additive, or during mixing. Brief Description of the Drawings

Figure 1 is a graph showing comparative LCM effects upon electrical stability in a field ECO-FLOW sample.

Figure 2 is a graph showing a particle size distribution analyses of CHECK- LOSS^® in various fluids.

Detailed Description of the Invention

Measurements of an emulsion-type drilling fluid are continually made in an effort to identify any loss in emulsion stability resulting from loss of circulation of the drilling fluid. A preferred method of measuring emulsion stability in invert emulsion drilling fluids is to measure the electrical stability of the drilling fluid.

The electrical stability of an oil-based drilling fluid relates both to its emulsion stability and to its oil-wetting capability. Electrical stability of a drilling fluid is determined by applying a voltage-ramped, sinusoidal electrical signal across a pair of parallel flat-plate electrodes immersed in the drilling fluid. The resulting current remains low until a threshold voltage is reached, whereupon the current rises very rapidly. This threshold voltage is the electrical stability of the drilling fluid and is defined as the voltage in peak volts-measured when the current reaches 61 μA.

Field operators monitor the emulsion stability of a drilling fluid by reading the voltage across the drilling fluid. The resulting electrical stability reading is directly related to the ratio of water to oil in a particular drilling fluid. As the concentration of water in the drilling fluid increases, the electrical stability value tends to decrease.

The reported decrease in electrical stability values in invert emulsion drilling fluids appears to be attributable to swollen, hydrated fibers of lost circulation material that come into contact with the electrical stability meter probe. In order to preserve electrical stability (and thereby emulsion stability), water wetting of such fibrous materials must be minimized.

The type of lost circulation material added to a particular drilling fluid varies according to the primary purpose of the drilling operation; the nature of the rocks to be penetrated; the site, and the skill and experience of the drilling crew. Various plant source fibers are used as lost circulation materials. Cellulose is a major constituent of most plant cell walls, and also has a high affinity for water. Without limiting the invention to a particular mechanism of action, the decrease in electrical stability of drilling fluids comprising many fibrous lost circulation materials is believed to be due to the intrinsic affinity of the cellulose in those fibers for water. In order to reduce the impact of a lost circulation material on electrical stability readings, the present invention reduces the cellulosic content of the fibrous material.

Lignin also is found in plant cell walls. Lignin is a strengthening polymer which provides rigidity and strength to the plant material. Lignin does not have as great an affinity for water as cellulose. Plant materials with higher lignin contents should have a directly or indirectly proportional decrease in affinity for water. It is difficult to analyze plant materials directly to determine their lignin content.

The present invention involves the use of "high lignin" lost circulation materials (HLLCM' s) in drilling fluids. HLLCM' s increase electrical stability values in emulsion type fluids, and thereby increase emulsion stability "HLLCM' s" are herein defined as fibrous lost circulation materials effective to maintain the electrical stability value of a given drilling, drill-in or completion fluid to within 20% or less of the electrical stability value of the same fluid in the absence of the HLLCM Preferred HLLCM' s are effective to maintain the electrical stability value of a given drilling, drill-in or completion fluid within 18% of the electrical stability value of the same fluid in the absence of the HLLCM, more preferably to within about 15%, and most preferably to within about 12% Another way of stating the electrical stability limitation is that the addition of the HLLCM causes a maximum reduction in voltage reading of 20% or less relative to the initial voltage reading, more preferably about 18%) or less, even more preferably about 15 % or less, most preferably about 12% or less

Suitable HLLCM' s may be identified with reference to their "Water Retention Value" (WRV) A given plant material has a given hydration rate based on the size of voids within the fibers of that plant material When the dry plant material is exposed to water, these voids are swollen by the water The swelling of these voids in the presence of water may be measured, and the measured value is known as the material's WRV The WRV is a measure of the amount of water intimately associated with a given dry weight of a given plant material, and is approximately equal to the total change in volume of the cell wall of the plant material

The WRV for a given plant material may be calculated upon performing a simple test Add 25 g test material to a glass jar Mix 250 ml of deionized water with the test material Shear the slurry at 3000 rpm for 5 min Cap the glass jar roll 16 hr

at 150°F After cooling, pour the jar contents into an assembled Buchner funnel (using Whatman filter paper No. 41) fitted on a 2-liter Erlenmeyer flask, hooked to a vacuum pump. Filter for two hours maximum. Remove the Buchner funnel with test material from the flask and weigh. Calculate the WRV using the following equation:

(Buchner funnel with filter (Buchner funnel with wet paper) - paper and retained wet test material)

Initial 25 g dry test material.

Fibrous lost circulation materials in current use have a calculated WRV of about 4 or more. HLLCM' s that are suitable for use in the present invention have a calculated WRV of 1 or less, preferably 0.5 or less, and more preferably 0.3 or less.

Examples of suitable HLLCM' s include, but are not necessarily limited to plants that actually grow in water but tend to remain dry, such as bulrush plants, which include cattails, papyrus, and the like. Also suitable are lignin byproducts derived from the processing of wood or other plant materials into paper. The products made from such processes typically require high contents of cellulose, and lignin is processed out of the wood. The lignin typically is sold for sulfo nation.

The HLLCM generally has a particle size distribution effective to form a filter cake and to block loss of circulation of the drilling fluid to the formation. Suitable particle size distributions generally are from about 10 μm to about 200 μm, preferably from about 15 to about 170.

A most preferred HLLCM for use in the invention is grape pumice. HLLCMs, preferably grape pumice, have the added advantage of inducing less impact upon rheological properties

The HLLCM preferably is used in emulsion type drilling fluids, most preferably invert emulsion drilling fluids. However, HLLCM' s are useful as a lost circulation materials in any type of drilling fluid, including water base fluids, natural or synthetic oil base fluids, oil-in-water emulsion fluids, and water-in-oil emulsion fluids.

The HLLCM may be included as an integral part of a drilling fluid, and/or added to a drilling fluid, as needed, during drilling operations. Where the HLLCM is used as an integral part of a drilling fluid, the quantity used is from about 0.1 ppg to about 25 ppg, preferably from about 5 ppg to about 10 ppg. Where the HLLCM is added to the drilling fluid as needed during operation, the HLLCM is simply added to the mud pit with mixing, as needed. The quantity of HLLCM added will vary depending upon the extent of the loss in circulation. Typically, the quantity is from about 0.1 ppg to about 25 ppg or more.

Alternately, the HLLCM is added to the mud pit as a spotting pill In this embodiment, the HLLCM is added as a slurry, together with a small amount of a carrier liquid that is compatible with the fluid being treated. A preferred slurry comprises from about 1 ppb to about 100 ppb HLLCM, preferably about 5 to about 50 ppb HLLCM. A most preferred spotting pill is from about 1 ppb to about 100 ppb grape pumice in a carrier fluid, preferably from about 5 to about 50 ppb grape pumice. Typically, after the HLLCM is spotted opposite the loss zone, it is desirable to pull into the casing and wait six to eight hours before continuing operations. Whether used as a integral part of the drilling fluid, or in a spotting pill, certain HLLCM' s, such as grape pumice, tend to increase the acidity of water base fluids. Hence, where the HLLCM is used in a water base fluid, it is preferred to add a sufficient quantity of a buffering agent to increase the pH to neutral, or about 7. Suitable buffering agents include but are not necessarily limited to soda ash, sodium bicarbonate, sodium hydroxide, lime, calcium hydroxide, and the like. A suitable amount of buffering agent is from about 0.1 lb to about 0.2 lb, preferably 0.1 lb, for every 10 lbs. HLLCM, preferably grape pumice.

Suitable carrier fluids for a spotting pill vary depending upon the fluid being treated. Where the fluid is a water base fluid, the carrier preferably will be aqueous. Where the fluid is an oil base fluid, the carrier preferably will be non-aqueous, and so forth. In a preferred embodiment, the carrier fluid is selected from the group consisting of glycols, polyglycols, polyalkyleneoxides, alkyleneoxide copolymers, alkylene glycol ethers, polyalkyleneoxide glycol ethers, and salts of any of the foregoing compounds, and combinations of the foregoing compounds.

Examples of suitable glycols and polyglycols include, but are not necessarily limited to ethylene glycols, diethylene glycols, triethylene glycols, tetraethylene glycols, propylene glycols, dipropylene glycols, tripropylene glycols, and tetrapropylene glycols. Examples of suitable polyalkyleneoxides and copolymers thereof include, but are not necessarily limited to polyethylene oxides, polypropylene oxides, and copolymers of polyethylene oxides and polypropylene oxides. Suitable polyalkyleneoxide glycol ethers include, but are not necessarily limited to polyethylene glycol ethers, polypropylene glycol ethers, polyethylene oxide glycol ethers, polypropylene oxide glycol ethers, and polyethylene oxide/polypropylene oxide glycol ethers. Preferred carriers are ethylene glycol, tripropylene glycol bottoms, and combinations thereof. A most preferred carrier is tripropylene glycol bottoms.

The invention will be better understood with reference to the following Examples, which are illustrative only. In the examples, CHEK-LOSS^® is a corn cob based LCM, available from Baker Hughes INTEQ; PHENO-SEAL^® is a ground plastic resin material, available from Montello, Inc.; MUD-LINER is a paper based LCM, available from BCI Incorporated; LIQUID CASING is a peanut hull based LCM available from Liquid Casing, Incorporated; KWIK SEAL FINE is a blend of vegetable and polymer fibers available from Kelco Oilfield Group; and BAROFIBRE is an almond hull based LCM, available from Baroid/Halliburton.

Example 1 Field operations personnel reported continuing problems of low electrical stability values for invert emulsion drilling fluids containing fibrous lost circulation material (LCM) additives. Although not identifying the specific additives, a report indicated that all fibrous materials lowered electrical stability values. However, HPHT fluid losses of the laboratory test muds showed no evidence of water. The criteria of absence of water in the HPHT filtrate was used as the preferred method of determining emulsion stability. The following is an assessment of the effects of various LCM additives on electrical stability, rheological properties, and HPHT PPA filtration control of synthetic-based fluids. EQUIPMENT

I . Prince Castle mixer 2. Fann visco meter, Model 35 A

3. Thermometer, dial, 0-220°F

4. Balance with precision of 0.01 g

5. Sieves (conforming to ASTM El l requirements)

6. Roller oven, 150 - 250 ± 5°F (66 - 121 ± 3°C) 7. Static aging oven

8. Wash bottle

9. Retsch grinding mill

10. Mortar and pestle

I I . Spatula 12 Timer interval, mechanical or electrical, precision of 0 1 minute

13 Jars (approximately 500 ml capacity) with sealing lids

14 Heating cup, OFI, 115 volt 16 Malvern Mastersizer

PROCEDURES

The following INTEQ Fluids Laboratory procedures were used: 7

• Recommended Practice Standard Procedure for Field Testing Oil-Based Drilling Fluids, API Recommended Practice 13B-2, Third Edition, February 1998 • Recommended Practice Standard Procedure for Field Testing Water-Based Drilling Fluids, API Recommended Practice 13B-1, Second Edition, September 1997

• Instrumentation Manual for Malvern Mastersizer

The following were the results

Tablel Comparative evaluation ofCHEK-LOSS® andBLEN-PLUG OM infield SYN-TEQ® samples

Table 2 Comparative evaluation of a) wetting agents with CHEK-LOSS® in afieldECO- FLOW and b com etitive brous LCM additives versus MIL-CΛRB® or PHENO-SEAL

Notes

• * Slurry blend prepared by mixing 0 86 bbl ISO-TEQ^®, 12 lb/bbl OMNI-COTE^® and 125 lb/bbl CHEK-LOSS^®, added 12 lb/bbl of sluπy (equivalent to 10 lb/bbl CHEK-LOSS) to base mud

• ** LCM blend prepared by mixmg 60% by weight MIL-GRAPHITE, 35% CHEK-LOSS^®, 2 5% WITCO 90 FLAKE and 2 5% INDUSTRENE R FLAKE

• ***LCP supplied by Environmental Drilling Technology (Tulsa, OK) Table 5 Performance of KWIK-SEAL Fine compared to CHEK-LOSS^® Coarse

Notes

*LCM additives ground by Retsch apparatus

Table 6 PPA STUDY - Evaluation of KWIK-SEAL^® Fine compared to CHEK-LOSS^® Coarse in a laboratory prepared 12 lb/gal SYN-TEQ^® fluid

Notes

*Base mud composition 0 629 bbl ISO-TEQ®, 12 lb OMNI-MUL®, 0 15 bbl water, 8 lb/bbl CARBO-GEL®, 18 lb calcium chlonde, 239 lb/bbl MEL-BAR® **LCM additives ground by Retsch apparatus

From the foregoing, it was concluded that the intrinsic affinity of cellulosic fibers for water was the cause of the influence of these fibers on electrical stability

Decreased electrical stability values were attributable to swollen, hydrated fibers coming into contact with the electrical stability meter probe The magnitude of the phenomenon was related to the amount of available water - i e the more water, the lower the value Therefore, the reduction in electrical stability increased as oil/water ratios decreased Water wetting of solids was never observed in the test fluids The bar chart of Fig 1 summarizes the variety of LCM effects upon electrical stability Particulate LCMs such as MIL-CARB® had no effect Mud property data is presented in the foregoing Tables, and in Fig 2

The following are oil mud evaluations detailing routine analytical results of submitted field mud samples used in the test matrices Table 7

Sample A

Sample Used For Drilling

Mud System Syn-Teq

Depth taken, feet 14800

External Phase-Oil Iso-Teq S G, Weight Mateπal 4 2

Mud Weight, lbm/gal 17 1 Density of Oil, lbm gal 6 6

Specific Gravity of Mud 2 05 Excess Lime, lbm/bbl 1 04

Rheologies @, °F 150 Total Calcium, mg/L mud 12000

600 rpm 98 Total Chloπdes, mg/L mud 26000

300 rpm 58 CaC12, mg/L mud 40820

200 rpm 44 CaC12, lbm/bbl of mud 14 29

100 rpm 28 CaC12, mg/L 402,797

6 rpm 8 CaC12, % by weight 31 2

3 rpm 7 Brine Density, g/ml 1 29

Plastic Viscosity, cPs 40 Corrected Brine, % by vol 10 1

Yield Point, lbf/100 ft² 18 Coπected Solids, % by vol 38 9

Initial Gel, lbf/100 ft² 9 Average Solids Density, g/ml 3 90

10 min Gel, lbf/100 ft² 12 Weight Matenal, % by vol 31 3

30 mm Gel, lbf/100 ft² 13 Weight Mateπal, lbm/bbl 460 0

API, mls/30 nuns Low Gravity Solids, % by vol 7 6

HT-HP Temp, °F 300 Low Gravity Solids, lbm/bbl 70 3

HT-HP, mls/30 nuns 2 2 Oil Water Ratio= Water 15 0

Pom, mls/lml mud 0 8 Oil Water Ratio=Oιl 85 0

AgN03, mls/lml mud 2 6 Coπected Water Ratio 16 6

EDTA, mls/lml mud 3 Coπected Oil Ratio 83 4

ES, volts 1200

Sohds, % by vol 40

Water, % by vol 9

Table 8

Sample E

Sample Used For Dnlhng

Mud System ECOFLOW 200

Depth taken, feet

External Phase-Oil Ecoflow S G, Weight Mateπal 4 2

Mud Weight, lbm/gal 16 6 Density of Oil, lbm/gal 6 6

Specific Gravity of Mud 2 00 Excess Lime, lbm/bbl 3 51

Rheologies @, °F 150 Total Calcium, mg/L mud 11200

600 rpm 82 Total Chloπdes, mg/L mud 24000

300 rpm 47 CaC12, mg L mud 37680 200 rpm 35 CaC12, lbm/bbl of mud 13 19

100 rpm 22 CaC12, mg/L 530,455

6 rpm 6 CaC12, % by weight 38 6

3 rpm 5 Brine Density, g/ml 1 38

Plastic Viscosity, cPs 35 Coπected Brine, % by vol 7 1

Yield Pomt, lbf/100 ft² 12 Coπected Solids, % by vol 39 9

Initial Gel, lbf/100 ft² 7 Average Solids Density, g/ml 3 71

10 nun Gel, lbf/100 ft² 11 Weight Mateπal, % by vol 27 2

30 nun Gel, lbf/100 ft² 11 Weight Mateπal, lbm/bbl 399 4

API, mls/30 mins Low Gravity Solids, % by vol 12 7

HT-HP Temp, °F Low Gravity Solids, lbm/bbl 118 1

HT-HP, mls/30 nuns Oil Water Ratio= Water 10 2

Pom, mls/lml mud 2 7 Oil Water Ratio=Oιl 89 8

AgN03, mls/lml mud 2 4 Coπected Water Ratio 11 8

EDTA, mls/lml mud 2 8 Coπected Oil Ratio 88 2

ES, volts 1360

Sohds, % by vol 41

Water, % by vol 6

Oil, % by vol 53

Table 9

Sample Number E

Sample Used For Drilling

Mud System Syn-Teq

Depth taken, feet

External Phase-Oil Eco-Flow 200 S G, Weight Mateπal 4 2

Mud Weight, lbm/gal 17 0 Density of Oil, lbm/gal 6 5

Specific Gravity of Mud 2 04 Excess Lime, lbm/bbl 5 46

Rheologies @, °F 150 Total Calcium, mg/L mud 14800

600 rpm 89 Total Chloπdes, mg/L mud 30000

300 rpm 52 CaC12, mg/L mud 47100

200 rpm 38 CaC12, lbm/bbl of mud 16 48

100 rpm 25 CaC12, mg/L 530,455

6 rpm 7 CaC12, % by weight 38 6

3 rpm 6 Brine Density, g/ml 1 38

Plastic Viscosity, cPs 37 Coπected Brine, % by vol 8 9

Yield Point, lbf/100 ft² 15 Coπected Solids, % by vol 38 1

Initial Gel, lbf/100 ft² 8 Average Solids Density, g/ml 3 94

10 mm Gel, lbf/100 ft² 12 Weight Mateπal, % by vol 31 7

30 mm Gel, lbf/100 ft² 13 Weight Mateπal, lbm/bbl 466 6

API, mls/30 nuns Low Gravity Solids, % by vol 6 4

HT-HP Temp, °F 300 Low Gravity Solids, lbm/bbl 59 1

HT-HP, mls/30 nuns 2 Oil Water Ratio= Water 12 4

Pom, mls/lml mud 4 2 Oil Water Ratio=Oιl 87 6

AgN03, mls/lml mud 3 Coπected Water Ratio 14 3 EDTA, mls/lml mud 3 7 Coπected Oil Ratio 85 7

ES, volts 1420

Sohds, % by vol 39 5

Water, % by vol 7 5

Oil, % by vol 53

Example 2

The following LCM's were obtained from Grinding & Sizing Co labeled as "Wood Fiber" (pine), "Grape Pumice", "Pith", "Furfural" and "Total Control" (ground rubber) Ground coconut shell was obtained from Reade Co in 325 mesh size and 80-325 mesh size ( "Reade 325F" and "Reade 325/80," respectively) EQUIPMENT

1 Prince Castle mixer

2 Fann viscometer, Model 35A 3 Thermometer, dial, 0-220°F

4 Balance with precision of 0 01 g

5 Sieves (conforming to ASTM El l requirements)

6 Roller oven, 150 - 250 ± 5°F (66 - 121 ± 3°C)

7 Spatula 8 Timer interval, mechanical or electrical, precision of 0 1 minute

9 Jars (approximately 500 ml capacity) with sealing lids

10 Heating cup, OFI, 115 volt

11 Particle Plugging Apparatus

12 Aloxite disks 13 Malvern Mastersizer

PROCEDURES

The following INTEQ Fluids Laboratory procedures were used

• Recommended Practice Standard Procedure for Field Testing Oil-Based Drilling Fluids, API Recommended Practice 13B-2, Third Edition, February 1998

• Recommended Practice Standard Procedure for Field Testing Water-Based Drilling Fluids, API Recommended Practice 13B-1, Second Edition, September 1997

• Instrumentation Manual for Malvern Mastersizer

The following results were observed TABLE 10: Evaluation of Various Fibrous LCM Additives from Grinding & Sizing Co., Inc., as compared to CHEK-LOSS

Oil-Mud Sample Evaluation Report (FSR No. 4502)

External Phase-Oil Ecoflow S G, Weight Mateπal 4 2

Mud Weight, lbm/gal 15 3 Density of Oil, lbm/gal 6 6

Specific Gravity of Mud 1 84 Excess Lime, lbm/bbl 1 95

Rheological Propertιes,°F 150 Total Calcium, mg/L mud 10400

600 rpm 60 Total Chlorides, mg/L mud 22000

300 rpm 35 CaC12, mg/L mud 34540

200 rpm 26 CaC12, lbm/bbl of mud 12 09

100 rpm 17 CaC12, mg/L 347,539

6 rpm 5 CaC12, % by weight 27 7

3 rpm 4 Brine Density, g/ml 1 25

Plastic Viscosity, cPs 25 Coπected Brme, % by vol 9 9

Yield Point, lbf/100 ft² 10 Coπected Solids, % by vol 35 1

Initial Gel, lbf/100 ft² 7 Average Solids Density, g/ml 3 65

10 mm Gel, lbf/100 ft² 10 Weight Matenal, % by vol 22 6

30 mm Gel, lbf/100 ft² 10 Weight Matenal, lbm/bbl 331 5

API, mls/30 mms Low Gravity Solids, % by vol 12 5

HT-HP Temp, °F Low Gravity Solids, lbm/bbl 116 0

HT-HP, mls/30 nuns Oil Water Ratio=Water 14 1

Pom, mls/lml mud 1 5 Oil Water Ratio=Oιl 85 9 AgN03, mls/lml mud 2 2 Corrected Water Ratio 15 3

EDTA, mls/lml mud 2 6 Corrected Oil Ratio 84 7

ES, volts 700

TABLE 11:

Evaluation of Grinding & Sizing Co. Grape Pumice, as compared to CHEK-LOSS, in a Solids-Laden Oil-Based Field Mud

TABLE 12:

Evaluation of Reade Co. Ground Coconut Shell, as compared to CHEK-LOSS, in a Solids-Laden Oil-Based Field Mud

The coconut materials had very minimal impact upon the electrical stability value of the base fluid However, these materials appeared to be kilned, thus making them more characteristic as a particulate rather than a fiber Resultant rheological properties were not satisfactory

In Data Tables 11 and 12, Formula 4522 was the following

Oil-Mud Sample Evaluation Report (FSR No. 4522)

External Phase-Oil Diesel S G, Weight Mateπal 4 2

Mud Weight lbm/gal 16 5 Density of Oil, lbm/gal 7 1

Specific Gravity of Mud 1 98 Excess Lime, lbm/bbl 1 30

Rheological Properties, °F 150, 120 Total Calcium, mg L mud 5200

600 φm 96, 137 Total Chloπdes, mg/L mud 9000

300 φm 52, 75 CaC12, mg L mud 14130

200 φm 36, 52 CaC12, lbm/bbl of mud 4 95

100 φm 21, 29 CaC12, mg/L 150,804

6 rpm 4, 5 CaC12, % by weight 13 6

3 φm 3, 4 Brine Density, g/ml 1 11

Plastic Viscosity, cPs 44, 62 Coπected Brine, % by vol 9 4

Yield Pomt, lbf 100 ft² 8, 13 Coπected Solids, % by vol 39 1

Initial Gel, lbf/100 ft² 5, 6 Average Solids Density, g/ml 3 67

10 mm Gel, lbf/100 ft² 21, 22 Weight Mateπal, % by vol 25 7

30 nun Gel, lbf/100 ft² 29, 30 Weight Mateπal, lbm/bbl 377 4

API, mls/30 mms Low Gravity Solids, % by vol 13 5

HT-HP Temp, °F 300 Low Gravity Solids, lbm/bbl 124 8

HT-HP, mls/30 mms 9 2 Oil Water Ratio= Water 14 9

Pom, mls/lml mud 1 Oil Water Ratio=Oιl 85 1

AgN03, mls/lml mud 0 9 Coπected Water Ratio 15 4

EDTA, mls/lml mud 1 3 Coπected Oil Ratio 84 6

ES, volts 650

Sohds, % by vol 39 5

Water, % by vol 9 TABLE 13:

Evaluation of Grinding & Sizing Co. Grape Pumice, as compared to CHEK-LOSS, in a Laboratory-Prepared Water-Based Mud

In Data Table 13, Formulation 4423b was the following

Grape Pumice appears to fulfill the needed characteristic of being composed of more lignin rather than cellulose. Grape Pumice caused significantly less impact (5 - 10% decreases) upon electrical stability values, as compared to 50 - 60% decreases when adding CHEK-LOSS. Grape Pumice also induced less impact upon the plastic viscosities of the oil muds, as compared to CHEK-LOSS. Grape Pumice provided better PPA (particle plugging apparatus) results, as compared to CHEK-LOSS at test conditions of 300°F, 1000 psi differential, 90-micron aloxite disk.

Example 3

The papermaking industry uses a measurement called the Water Retention Value (WRV), which gives the amount of water intimately associated with a given dry weight of wood pulp. This represents the capacity of fibers to swell in the presence of water. This value varies with the source of plant fibers (corn, peanut, walnut, almond, coconut, etc.). The paper industry wants more cellulose, less lignin. The need in this application is to choose a plant fiber source with a ratio of more lignin with less cellulose. Lignin, which serves as the "skeletal" structure for plants, is significantly less water-absorbent.

The following described procedure is a modification of the TAPPI 1991 UM- 256 procedure used in the papermaking industry. Equipment used included:

1. Prince Castle mixer

2. Tachometer

3. 500-ml glass jars with lids

4. Deionized water 5. Electronic balance

6. Vacuum pump

7. 2-liter Erlenmeyer flask

8. Buchner funnel

9. Whatman filter paper No. 41 An amount of 25 g test material was added to a glass jar. 250 ml of deionized water was then added. The slurry was sheared at 3000 rpm for 5 min. The glass jar was

capped and rolled 16 hr at 150°F. After cooling, the jar contents was poured into an

assembled Buchner funnel (using Whatman filter paper No. 41) fitted on a 2-liter

Erlenmeyer flask, hooked to a vacuum pump. Filtration was conducted for two hours maximum. The Buchner funnel with test material content was removed from the flask and was weighed. Calculation of the WRV would be as follows:

(Buchner funnel with filter paper and retained wet test material minus Buchner funnel with wet paper) minus initial 25 g dry test material. Resultant value then divided by initial 25 g dry test material.

Results were, as follows:

The Grape Pumice material appears to fulfill the needed characteristic of being composed of more lignin rather than cellulose.

Particle size analyses by Malvern Mastersizer instrumentation showed the Grape Pumice to be near-similar to CHEK-LOSS:

As evident by this data, particle size distribution would not contribute to differentiating WRV between the two materials; Grape Pumice exhibits significantly less water absorbency, a characteristic favorable for application as a LCM in invert emulsion drilling fluids while not interfering with emulsion stability measurements. Example 4

The Grape Pumice material, being acidic, will lower pH levels in aqueous muds. A test was conducted by adding 10 lb Grape Pumice to a 1-bbl equivalent of deionized water. Resultant pH was 3.5. Blending 10 lb Grape Pumice with 0.2 lb soda ash kept the pH at 7.0. Because of this concern, alkalinity levels were measured in the oil muds tested with Grape Pumice. There were no changes, thus the Grape Pumice seems to be preferentially oil-wetted.

Persons of ordinary skill in the art will recognize that many modifications may be made to the present invention without departing from the spirit and scope of the invention. The embodiment described herein is meant to be illustrative only and should not be taken as limiting the invention, which is defined in the claims.

Claims (1)

1. We claim: 1. A method for maintaining electrical stability in an emulsion type drilling, drill-in, or completion fluid comprising lost circulation material (LCM), said method comprising: providing an initial fluid selected from the group consisting of an emulsion- type drilling, drill-in, or completion fluid, said initial fluid having effective rheology and fluid loss control properties; using a fibrous LCM in said initial fluid, said fibrous LCM consisting essentially of a quantity of high lignin lost circulation material (HLLCM), said fibrous HLLCM being effective to produce a treated fluid having effective rheology and fluid loss control properties; wherein said initial fluid exhibits a first electrical stability value and said treated fluid exhibits a second electrical stability value that is a maximum of 20% less than said first electrical stability value. 2. A method for maintaining electrical stability in a drilling, drill-in, or completion fluid, said method comprising: providing an initial fluid selected from the group consisting of an emulsion type drilling, drill-in, or completion fluid having effective rheology and fluid loss control properties; and using as LCM in said initial fluid a fibrous HLLCM having a water retention value of about 1 or less, said HLLCM being effective to produce a treated fluid having effective rheology and fluid loss control properties. 3. A treated emulsion type fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said emulsion type drilling fluid having effective rheology and fluid loss control properties and comprising a lost circulation material consisting essentially of an HLLCM, said wherein said emulsion type fluid exhibits a first electrical stability value and said treated emulsion type fluid exhibits a second electrical stability value that is a maximum of 20% less than said first electrical stability value 4 A treated emulsion type fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having effective rheology and fluid loss control properties and consisting essentially of an LCM having a water retention value of about 1 or less 5 A treated emulsion type fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having effective rheology and fluid loss control properties and comprising a fibrous LCM, said fibrous LCM consisting essentially of materials selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from the processing of plant material into paper 6 A spotting pill comprising from about 1 to about 100 ppb of an HLLCM and a carrier liquid, wherein a given emulsion type fluid exhibits a first electrical stability value absent said spotting pill and said given emulsion type fluid comprising said spotting pill exhibits a second electrical stability value that is a maximum of 20% less than said first electrical stability value 7 A spotting pill comprising from about 1 to about 100 ppb of an HLLCM and a carrier liquid, wherein said HLLCM has a water retention value of about 1 or less 8 A spotting pill comprising from about 1 to about 100 ppb of an HLLCM and a carrier liquid, wherein said HLLCM consists essentially of materials selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from the processing of plant material into paper. 9. A spotting pill comprising from about 1 to about 100 ppb grape pumice and a carrier liquid. 10. The method of any of claims 1-2, the treated emulsion type fluid of any of claims 3-5, or a treated emulsion type fluid comprising a given emulsion type fluid comprising the spotting pill of any of claims 6-9, wherein said given emulsion type fluid exhibits a first electrical stability value and said treated emulsion type fluid exhibits a second electrical stability value that is a maximum of 20% less than said first electrical stability value. 11. The method or treated emulsion type fluid of any of claims 1-5 or 10 wherein said second electrical stability value is a maximum of 18% less than said first electrical stability value. 12. The method or treated emulsion type fluid of any of claims 1-5 or 10 wherein second electrical stability value is a maximum of 15% less than said first electrical stability value. 13. The method or treated emulsion type fluid of any of claims 1-5 or 10 wherein said second electrical stability value is a maximum of 12% less than said first electrical stability value. 14. The method, treated emulsion type fluid, or spotting fluid of any of claims 1, 3, 5-6, or 8-13 wherein said fibrous HLLCM has a water retention value of about 1 or less. 15 The method, treated emulsion type fluid, or spotting fluid of any of claims 1-14 wherein said fibrous HLLCM has a water retention value of about 0 5 or less 16 The method, treated emulsion type fluid, or spotting fluid of any of claims 1-5 wherein said fibrous HLLCM has a water retention value of about 0 3 or less 17 The method, treated emulsion type fluid, or spotting fluid of any of claims 1-16 wherein said emulsion type drilling, drill-in, or completion fluid is an invert emulsion type fluid 18 The method, treated emulsion type fluid, or spotting fluid of any of claims 1-4, 6-7, or 10-17 wherein said HLLCM is selected from the group consisting of grape pumice, bulrush plants, and lignin byproducts from processing plant material into paper 19 A method for maintaining electrical stability in a drilling, drill-in, or completion fluid, said method comprising providing an initial fluid selected from the group consisting of a emulsion type drilling, drill-in, or completion fluid, said initial fluid having effective rheology and fluid loss control properties, and using an LCM in said initial fluid, said LCM consisting essentially of grape pumice effective to produce a treated fluid having effective rheology and fluid loss control properties 20 A treated emulsion type fluid selected from the group consisting of a drilling, drill-in, or completion fluid, said fluid having effective rheology and fluid loss control properties and comprising a fibrous LCM consisting essentially of grape pumice. 21. The method or treated emulsion type fluid of any of claims 19-20 comprising an invert emulsion fluid. 22. The method, treated emulsion type fluid, or spotting fluid of any of claims 1-21 wherein said HLLCM comprises a particle size distribution of from about 10 μm to about 200 μm. 23. The spotting pill of any of claims 6-22 comprising from about 5 to about 50 ppb of said HLLCM. 24. The spotting pill of any of claim 6-23 wherein said carrier liquid is selected from the group consisting of polyalkylene oxides and copolymers thereof, polyalkyleneoxide glycol ethers, glycols, polyglycols, tripropylene glycol bottoms, and combinations thereof. 25. The spotting pill of any of claims 6-23 wherein said carrier liquid is selected from the group consisting of ethylene glycols, diethylene glycols, triethylene glycols, tetraethylene glycols, propylene glycols, dipropylene glycols, tripropylene glycols, tetrapropylene glycols, polyethylene oxides, polypropylene oxides, copolymers of polyethylene oxides and polypropylene oxides, polyethylene glycol ethers, polypropylene glycol ethers, polyethylene oxide glycol ethers, polypropylene oxide glycol ethers, and polyethylene oxide/polypropylene oxide glycol ethers. 26. The spotting pill of any of claims 6-23 wherein said carrier liquid is selected from the group consisting of ethylene glycol, tripropylene glycol bottoms, and combinations thereof.

   27. A spotting pill comprising from about 1 to about 100 ppb of an HLLCM and a carrier liquid comprising tripropylene glycol bottoms. 28. A spotting pill comprising from about 1 to about 100 ppb of an HLLCM comprising grape pumice and a carrier liquid comprising tripropylene glycol bottoms. 29. The spotting pill of any of claims 27 or 28 comprising from about 5 to about 50 ppb of said HLLCM.