API St 65-2-2010 pdf download.Isolating Potential Flow Zones During Well Construction.
In some cases, pre-spud information gathered from offset well(s) and/or from high resolution seismic surveys can be used to indicate flow potential for a particular drilling prospect. Any relevant information should be communicated to the appropriate service provider for incorporation into the design for a particular fluid (drilling fluid or cement) and for preparing engineering and operations procedures. 1.6 Drilling the Well Annex C gives a general overview of drilling the well and some of the factors that might be considered by the drilling group. Some of those factors may include general practices while drilling, monitoring and maintaining wellbore stability, mitigating lost circulation, and planning and operational considerations. There may be other factors to consider such as type and location of the well being drilled. These factors should be considered during the drilling of the well to enhance the barrier sealing performance. Detailed discussion of these factors is included in Annex C and may be mentioned in other sections. 1.7 Summary of Considerations Isolating a potential flow zone with cement is an interdependent process. Individual process elements such as slurry design and testing, applied engineering and job execution all impact the ability to successfully install a cement barrier. Superimposed upon these elements are the conditions found in the well at the time of cementing. Certain cementing process elements contained in Annex D may be individually critical to isolating a potential flow zone or may be of minor consequence until made critical by a separate (sometimes unrelated) event or past well engineering decisions. Conversely, certain elements may not be dominant factors in the success in one cementing operation, yet vitally important in another. Collectively, the elements described in Annex D produce the design, engineering and operational framework for successfully isolating a potential flow zone.
3 Definitions, and Abbreviated Terms 3.1 Definitions For the purposes of this document the following terms and definitions apply. In addition to those listed below other definitions and abbreviations may be found in oilfield glossaries at websites listed in the Bibliography. [47,48,49,50,51] 3.1.1 ambient pressure Pressure external to the wellhead. In the case of a surface wellhead it would be 0 psig. In the case of a subsea well head, it would be equal to the hydrostatic pressure of seawater at the depth of the subsea wellhead in psig. 3.1.2 annular flow The flow of formation fluids (liquids and/or gases) from the formation into a space or pathway in an annulus within a well. The annular flow may follow various flow paths inside the annulus to other points including those at shallower or deeper depths. 3.1.3 annular packers and seal rings Mechanical barrier devices with flexible, elastomeric sealing elements that can be run into a well on casing or liners for application as: a) annular element installed between an inner and outer pipe or between a casing and openhole formation to seal the annulus, b) annular seal rings installed on the inner pipe string to seal the micro-annulus and voids formed between the cement sheath and the inner pipe string.
3.1.6 annulus The space between the borehole and tubulars or between tubulars, where fluid can flow. The annulus designation between the production tubing and production casing is the “A” annulus. Outer annuli between other strings are designated B, C, D, etc. as the pipe sizes increase in diameter. 3.1.7 barrier (barrier element) A component or practice that contributes to the total system reliability by preventing liquid or gas flow if properly installed. 3.1.8 blowout preventer BOP A device attached to the casing head that allows the well to be sealed to confine the well fluids in the wellbore. Refer to API RP 53 or other relevant standards for further information. 3.1.9 borehole Wellbore sections which are not cased with pipe, commonly called open hole. 3.1.10 bottom hole assembly BHA Bottom hole assembly is the collection of the bit, drill collars, stabilizers, reamers, hole openers, MWD/LWD/PWD, mud motor, directional steering system and other tools at the base of the drill string that serve special purposes associated with drilling. 3.1.11 cased hole The wellbore intervals in a well that are cased with casing and/or liner pipe. The diameter of these hole sections is the inside diameter of the pipe contained therein.