Reservoir Formation Damage Episode 3 Part 10 ppsx

Formation Damage Control and Remediation 707

cases, such as open hole completions (Bennion, 1999). Because formation

damage is usually nonreversible, it is better to avoid formation damage

rather than deal with it later on using expensive and complicated pro￾cedures (Porter, 1989; Mungan, 1986). In many cases, remedial treatments

may also cause other types of damages, while the intent is to cure the

present damage problems. When asked "Is it more cost effective to

prevent formation damage or bypass it?" (JPT, ©1994 SPE; reprinted by

permission of the Society of Petroleum Engineers), some experts replied

as following:

McLeod: "There is no universal answer for this question. Often the

formation quality determines whether it is more cost effective to

prevent damage or to remove it or bypass it later by acidizing or

hydraulic fracturing. Generally, damage prevention is more cost

effective than removing or bypassing damage later."

Peden: "Prevention of damage must be cost effective but it requires

a greater understanding of the physics of the processes, as well as

an improvement both in our predictive and operational techniques.

Bypassing damage can never be an attractive alternative to damage

minimization."

Penberthy: "If it is more cost effective to prevent damage, then that

is probably the best solution. If an effective, inexpensive acid job or a

minifrac treatment is less expensive than the cost of the completion

fluid, the post-treatment approach probably should be selected."

Some of the other comments of the experts are quoted in the following

from JPT (1994):

Burnett: "If there is existing formation damage in a well, there are three

choices: live with it; fracture or perforate past it; or use some means

of removing it. The choice depends upon economics and technology.

The key to formation damage cleanup is understanding what has

caused the damage. The damage may be caused by tenacious filter

cakes, particle invasion into the rock, and/or fluid-filtrate chemical

damage. Many of us believe that particulate damage extends only

a few tenths of a foot into a zone. On the other hand, chemical

damage (clay reactions, formation fines movement, rock/fluid incom￾patibility, and precipitation) can exist tens of feet into the pay zone.

Near-well damage can be reduced (but not eliminated) with acids,

oxidizers, and solvents. If you have deep damage, then sidetracking

is nearly always the best option."

708 Reservoir Formation Damage

Peden: "The further we get away from the borehole, the less control

we have over our ability to clean up or remove impairment . . .

However, formation damage is largely characterized by a lack of

understanding of the potential of the processes and the mechanisms

involved . . . Greater understanding, training, and technology transfer

is required between the service and operating-company sectors."

Penberthy: "One of the main causes for formation damage is using

techniques, procedures, and fluid systems that are known to cause

problems and risking the chance that somehow the operator will be

able to "get by with it."

Whether a particular fluid is nondamaging depends on the par￾ticular site-specific application and formation in which the well is

completed; i.e., there may be no such thing as a universal non￾damaging completion fluid. Suggestions are to use clear brines that

are compatible with the reservoir rock.

I will specify the guidelines for selecting an ideal fluid. While it

may be rare that all properties can be achieved, compromising

between fluid properties and characteristics should identify com￾pletion fluids that will provide acceptable results.

An ideal completion fluid should be compatible with the reservoir

rock (nondamaging) and have low fluid loss, acceptable suspension

and transport properties, thin filter cake, and low friction loss. The

density should be easily controlled. The fluid should also be readily

available, inexpensive, easily mixed and handled, and nontoxic."

Ali: "All brine systems are potentially formation damaging at high

temperatures. In addition, unfavorable fluid/rock interaction at

relatively low temperature can produce mobile fines with the added

potential for the precipitation of carbonate, sulfide, sulfate, and

sodium-chlorite scales. The need for thoroughly evaluating the

compatibility of completion fluids with formation brine, formation

mineralogy, and produced fluids cannot be overly stressed."

Burnett: "In fields we have studied, we've found that formation

damage from water-based fluids was no worse than corresponding

oil-based or synthetic fluids. The key is ensuring that the fluid,

whatever it may be, is compatible with the formation fluids and the

rock matrix."

McLeod: "In high-permeability formations, polymers and other

fluid-loss control materials can cause severe damage if not mixed

properly. Sometimes that damage may be removed by appropriate