Purposes of oil well cementing are as follows:
Zonal Isolation: Isolate hydrocarbon pays, water pays, shale, etc.
Seal off lost circulation zones
Hydraulic Seal: Prevent pressure from the undesirable migration of fluid coming up to surface via annulus between casing and hole.
Protect casing: Cement is a protective sheath around casing.
Hold casing and completion string: Cement supports weight of whole string of casing or completion.
The importance to accomplish the primary oil well cementing is as follows:
Good reservoir management: Good cement will let engineer design to produce hydrocarbon from reservoirs easier because there is no concern related to cement.
Maximize Reserves: Good cement sheath allows good pay sands to produce as maximum as possible because good sands will stop producing earlier due to water load-up or permeability damage.
Save time and cost: A lot of time and money must be spent to perform remedial cement operation which is cement squeeze job by coiled tubing or Hydraulic Work Over. If primary cement can be accomplished, no more time and money is spent out to do remedial work.
The key factors necessary to ensure a successful primary oil well cement job are as follows:
1. Good information: Related information such as calculated hole diameter, hole volume, depth, etc from related personnel is required in order to design cementing programs.
2. Good cementing design: There is a number of cement purposes such as primary cement, cement squeeze, cement plug. To meet the purpose of each job, cementers must design a cementing program in correct and good way.
3. Good procedures: Clear and concise procedure will lead to good job because cementer and assistants can perform the cementing job correctly, fast, safely.
4. Good equipment and experienced personnel: Experienced staff with good equipment can perform great jobs, no lost time, safe and fast.
5. Good centralizer placement: Centralizers help casing in the center of hole. Casing with good centralizer placement, cement can form properly cement sheath around casing.
Ref books: Cementing Technology Books