6. Standard Procedure:
The purpose of different standards is to provide operators a specific guideline to perform different inspection by reducing the possible Inspection errors. To accomplish this, users of this standard establish specific rules to govern the inspection process. Taken together, these rules become the "Inspection Program". The inspection program defines:
(a) Which inspection methods will be applied to each drill stem component.
(b) How each inspection method must be conducted in a step-by-step procedure.
(c) What acceptance criteria will be in effect during inspection - that is, the user's definition of "good" and "bad".
Communication:
In addition to errors caused by the inherent limitations of inspection tools and procedures, many inspection errors occur because the inspection buyer does not know or does not spell out his exact requirements. Two common phrases should be avoided because their meaning is undefined and ambiguous:
(a) "API Inspection" is an often used but ambiguous phrase. The attributes of acceptable used drill stem components can be found in API RP7G for many types of equipment. However, that standard is essentially silent on how those attributes are to be evaluated. Therefore, the phrase "API Inspection" has no real universally understood meaning.
(b) "DS-1 Inspection" is likewise a meaningless phrase when used alone. A DS-1 inspection can vary from very little (Cat 1) to a great deal (Cat 5). Therefore, for the term "DS-1 Inspection" to have a precise meaning, a category must also be stated. The term "DS-1, Cat 3" (for example) exactly establishes the inspection program and process quality controls that the inspector must use on certain equipment.
7. What are the Solutions?
i) Failure Analysis:
Group 1 Failure: if stress in a component exceeds some fairly high stress threshold. The threshold stress is also used for setting minimum acceptable dimensions for a component when the maximum load is fixed.
Group 2 Failure: can occur at low stress levels and heavily influenced by the drilling mud chemical environment and accumulated fatigue.
The response to a drill stem failure also depends on whether the failure mechanism is Group 1 or Group 2.
In the planning phase of a well, the approach to preventing failures depends on whether the Failure mechanism is Group 1 or Group 2.
Example 1: "All wells in District A shall be inspected to DS-1 Category 3".
Example 2: "Service category shall be determined independently based on depth, mud weight, well location, and H2S concentration according to the following table. The highest service category shall be used to set the inspection program".
Offshore, inland water or remote locations, use minimum Service Category 4. For formation H2S concentrations greater than 0.05 psia, use Service Category 5.
ii) Tubular Management System
Evolution of a highly effective Tubular Management System can only be possible by good coordination and frequent communication between
a) Oil Operating Company
b) Drilling Contractor
c) Inspection Service Company.
All these three parties should work together from the design stage of the proposed well Design Objectives are to
a) Keep the maximum stress at any point in the drill stem less than yield strength down-rated by a design (safety) factor;
b) Select components and configure assemblies to retard fatigue as much as economically practical.
