Practical Approaches for Solving Lost Circulation Problems While Drilling

Practical Approaches for Solving Lost Circulation Problems While Drilling

CHAPTER ONE

RESEARCH OBJECTIVES

The objectives of this study are as follows:

To review lost circulation control methods that have been applied in the drilling industry till
To provide the successes and the failures of the methods presented above in field
To develop practical guidelines that will serve as a reference material for lost circulation control at the well-site for drilling

FUNDAMENTALS OF LOST CIRCULATION CONTROL

A lot of effort has been done to understand the mechanics of lost circulation control. Lost circulation control during well construction is more than just selecting the right lost circulation material (LCM) but requires a complete engineered approach (Whitfill, 2008). Some of the approaches involve borehole stability analysis, equivalent circulating density (ECD) modelling, leak-off flow-path geometry considerations, drilling fluid and LCM selection to help minimize effects on ECD, on-site monitoring using annular pressure while drilling (APWD), connection flow monitoring techniques, and timely application of LCM and treatments. This chapter sheds light on the physics and chemistry of some of the lost circulation control approaches.

LOST CIRCULATION MATERIALS (LCMs) SELECTION

LCMs are needed to stop fluid losses in order to drill ahead in most drilling operations. An LCM should react, block fractures, and form a bridge to provide a seal in a timely manner. The seal could be temporary or even permanent. Permanent seals are used to block thief zones in non-producing intervals while temporary seals are used to block loss zones in pay intervals (Fidan et al. 2004). Previous studies have demonstrated that some products work better than others as lost circulation materials (Sanders et al. 2010). LCMs are categorized into common groups along their physical and chemical characteristics. These groups are as follows (Onyekwere, 2002):

Conventional Lost Circulation Materials; (fibers, flakes, andgranules)
High Fluid Loss Squeezes; (diatomaceous earth or clayblends)
Gunk Slurries; (diesel oilbentonite)
Precipitated Chemical Slurries; (silicate andlatex)
Resin-coatedSand
Cross-linked PolymerSlurries
Cements
Barite Plugs
DilatantSlurries

Conventional LCMs

These LCMs can be classified as granular (ground walnut shells, pecan shells, almond shells, plastic, and calcium carbonate), flakes (ground mica, plastic laminate, cellophane, and polyethylene plastic chips), fibers (rice hulls, peanut hulls, wood, cane etc.) or a mixture of the three. The granular LCMs form two types of bridges; one at the formation face and one within the formation matrix. The latter sealing is preferred because it forms a more permanent bridge within the formation such that pipe movements in the wellbore cannot dislodge the granular particles. The effectiveness of granular LCMs depends on their particle size distribution, with larger particles first forming a bridge across or within the void and smaller particles bridging the openings between larger ones. Fibrous materials are best suited for controlling losses in porous and highly permeable formations because they form a mat-like bridge over the pore openings. The mat reduces the size of the openings to the formation, permitting the colloidal particles in the mud to rapidly deposit a filter cake. Flake LCMs are also designed to form a mat on the formation face, which also provides the best results as fibrous materials when used to treat losses in porous and highly permeable formations. Blends of granular, flakes, and fibrous materials are used in solving actual field problems (Pilehvari and Nyshadham, 2002).

CHAPTER THREE

REVIEW OF LOST CIRCULATION CONTROL METHODS/TECHNIQUES

Lost circulation solutions may be applied before or after the occurrence of the problem (Wang et al. 2009). The solutions are therefore grouped into preventive and remedial respectively. This chapter highlights some of the lost circulation control methods/techniques that are used in the petroleum industry.

USING LOST CIRCULATION MATERIALS (LCMs)

A wide range of bridging or plugging materials is available for reducing lost circulation or restoring circulation while drilling or cementing a well (Nayberg and Petty, 1986). The choice of LCM to use in a given case depends on cost and availability in a given drilling area (Pilehvari and Nyshadham, 2002). LCMs are designed to accomplish two goals (Jiao and Sharma, 1996):

To bridge across the face of fractures and vugs that already
To prevent the growth of any fractures that may be induced while

Lost circulation materials can be broadly classified into the following groups (Suyan et al.2007; Pilehvari and Nyshadham, 2002):

Granular: these LCMs form bridges at the formation face and within the formation matrix, thus providing an effective seal which depends on the particle size distribution(PSD).
Fibrous: these groups of LCMs are used in drilling muds to lessen mud loss in fractures and vugular
Flakes: flaky types of LCMs are used to plug and bridge many types of porous formations to stop the mud loss or to establish an effective seal over many permeable
Mixtures: these are combinations of granular, flaky and fibrous materials that will penetrate fractures, vugs, or extremely permeable formations and seal them off
Encapsulated fluid-absorbing particles: these are materials that are highly absorbent and form spongy mass in contact with

Detailed classification of LCMs has been covered in chapter 2 of this thesis. From a review of various literatures on lost circulation, it can be inferred that a combination of LCMs rather than one is effective in combating losses. Table 3.1 provides some commonly used LCMs.

CHAPTER 4

PRACTICAL GUIDELINES TO COMBAT LOST CIRCULATION WHILE DRILLING

GENERAL GUIDELINES

The drilling program must include contingency plans (additional casing strings, adequate water source etc.) for known problems such as that associated with infill drilling and unknown problems such as those encountered in wildcat
The following information is required about the loss zone before an effective treatment could beachieved:
1. The location of the loss interval – preferably the top and
2. Estimate the pressure within the loss
3. Estimate the size of the openings into the loss zone; use borehole electronic
4. Knowledge of whether or not there is cross-flow into the loss zone because of the reduced pressure in the wellbore. Cross-flows into the loss zone can complicate the treatment
A quick economic evaluation should be made of how much investment would go into curing the lost returns problem before a decision is made to case the zone off, or side-track the loss interval or even abandon the
It is important to reduce human error, to a tolerable minimum, as a contributing factor to lost circulation.The following drilling practices were identified as contributing to lost circulation:
Generation of excessive ECDs caused by high circulation rates (Prevention strategy: Use the lowest circulation rate that will clean the holeadequately).
Failure to break circulation frequently while tripping (Prevention strategy: Break circulation several times on the way into the hole and rotate the pipe; when on the bottom, break circulation slowly, and raise the pipe while doingso).

CHAPTER FIVE

SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS

SUMMARY

Lost circulation presents a lot of challenges while drilling. To address these problems, a number of methods/techniques have evolved over the years. The objectives of this study are: 1) to review lost circulation control methods that have been applied in the drilling industry till date

2) to provide the successes and the failures of these methods in field applications and 3) to develop practical guidelines that will serve as a reference material for lost circulation control at the well-site for drilling personnel.

To achieve these study objectives, a selected number of technical journals, papers, textbooks, and manuals that address the problem of lost circulation were carefully reviewed and summarized. The results of this study are practical guidelines that are not biased towards a particular service industry product but are general to the mitigation of the problem of lost circulation while drilling. A flow chart has also been developed that will serve as a quick reference guide for drilling personnel at the well-site.

CONCLUSIONS

Based on this study, the following conclusions were made:

Successful control or treatment of lost circulation depends on several factors such as borehole temperature, pressure, depth, and size of the thief
There are no guaranteed methods for solving lost circulation problems entirely but a lot of approaches can be used to prevent its occurrence, especially those that occur via induced fractures when drilling formations that are prone to
Practical guidelines have been developed that when used with the accompanying flow chart will serve as a quick reference guide to prevent and minimize the problem of lost circulation while drilling.

RECOMMENDATIONS

For future work in this study area, the following recommendations may be considered:

The effect of lost circulation materials (LCMs) on reservoir productivity may be considered when selecting these materials for lost circulation
Since the subject of lost circulation control is very broad, a study may be conducted in a particular formation type, such as depleted reservoirs, for in-depth understanding of control measures.

REFERENCES

Aadnoy, B.S., Belayneh, M., Ariado, M., and Flateboe, R.: “Design of Well Barriers To Combat Circulation of Losses,” paper SPE 105449 presented at the 2007 SPE/IADC Drilling Conference and Exhibition held in Amsterdam, The Netherlands, 20-27 February.
Abbas, R., Jarouj, H., Dole, S., Effendhly, Junaidi, H., El-Hassan, H., Francis, L., Hornsby, L., McCaith, S., Shuttleworth, N., van der Plas, , Messier, E., Munk, T., Nadland, N., Svendsen, R.K., Therond, E., and Taoutaou, S.: A Safety Net for Controlling Lost Circulation. Oilfield Review (winter, 2003/2004)20.
Abrams, A.: Mud Design to Minimize Rock Impairment Due to Particle Invasion. JPT (May, 1977)
Beda, G., and Carugo, : “Use of Mud Microloss Analysis While Drilling to Improve the Formation Evaluation in Fractured Reservoir,” paper SPE 71737 presented at the 2001 SPE Annual Technical Conference and Exhibition held in New Orleans, Louisiana, 30 September – 3October.
Bell, R.J., and Davies, J.M.: “Lost Circulation Challenges: Drilling Thick Carbonate Gas Reservoir, Natuna D-Alpha Block,” paper SPE/IADC 16157 presented at the 1987 SPE/IADC Drilling Conference held in New Orleans, LA, 15-18
Bruton, J.R., Ivan, D., and Heinz, T.J.: “Lost Circulation Control: Evolving Techniques and Strategies to Reduce Downhole Mud Losses,” paper SPE 67735 presented at the 2001 SPE/IADC Drilling Conference, Amsterdam, The Netherlands, 27 February – 1March.
Canson, B.E.: “Lost Circulation Treatments for Naturally Fractured, Vugular, or Cavernous Formations,” paper SPE/IADC 13440 presented at the 1985 SPE/IADC Drilling Conference held in New Orleans, Louisiana, 6-8
Carlton, L.A, and Chenevert, M.E.: “A New Approach to Preventing Lost Returns,” paper SPE 4972 presented at the 1974 49^thAnnual Fall Meeting of the Society of Petroleum of AIME held in Houston, Texas, 6-9

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