Mr. Erik Milito - The House Committee on Natural Resources ...

ISOLATING POTENTIAL FLOW ZONES DURING WELL CONSTRUCTION 35
5.9.5 Executing as Designed
Deviations from the planned job design can result in failure to meet the objectives of the cement job. It is
recommended that the job design is communicated with all key personnel prior to job execution. Contingency plans
that address surface and downhole equipment malfunctions, bulk delivery problems, losses etc. should also be
prepared and disseminated.
Pumping the cement job with the designed pump rates is important but density control should not be sacrificed to
obtain a planned rate. From a drilling fluid removal standpoint, flow rate only becomes critical once the spacer/preflush
has entered the annulus which often occurs during displacement, after mixing of cement has been completed. A
computer simulation can be used to determine a range of pump rates to optimize placement efficiency (see 5.6.5.8).
5.9.6 Pipe Movement
Pipe reciprocation and rotation can assist in effective drilling fluid removal. Pipe movement assists in drilling fluid
removal by altering the flow path of the drilling fluid, spacer(s), and cement slurry. Pipe movement can also help to
break the gel strengths of drilling fluid that may otherwise be bypassed by the spacer and slurry. Reciprocation should
be done slowly to ensure that surge pressures are minimized and losses are not induced due to fracturing of
formations. Computer surge programs can supply the maximum reciprocation rate during a cement job.
Proper equipment should be utilized anytime pipe movement is planned. When reciprocating, ensure that enough
treating iron has been installed from the rig floor to the cementing plug container. Pipe rotation necessitates the use of
equipment designed to rotate without creating stress on the plug container and treating iron.
5.9.7 Data Acquisition
All pertinent job data should be monitored and recorded by computerized data acquisition equipment. <strong>The</strong> data to be
recorded should include density of all fluids pumped, rate at which they were pumped, and surface treating pressure.
Pressure and rate should be recorded during the entire displacement, regardless of whether cement pumps or rig
drilling fluid pumps are used to displace the plug. If possible, return rates should also be recorded.
<strong>The</strong> recorded job data discussed in this section is necessary as a quality control record and for post job analysis and
reporting. It can also supply valuable information in the event that the job cannot be pumped as planned.
5.9.8 Lost Circulation Contingency Plans
Lost circulation contingency plans should be discussed prior to job execution (see A.10). <strong>The</strong>se plans can include
increasing or decreasing cement volumes, altering cement thickening times, altering fluid loss control of the slurry,
and increasing or decreasing slurry pumping and displacement rates. Computer aids such as surge analysis
programs and ECD programs can minimize the risk of lost circulation. In addition, there are several float equipment
designs that can be used to help reduce the risk of fracturing formations while running the casing into the wellbore.
5.9.9 Spacers and Pre-flushes
Spacers and pre-flushes play a key role in proper cement placement so it is very important that they are mixed and
pumped as designed.
Pre-flushes are not densified and usually contain only a low concentration of a few additives so they can be easily
mixed on-the-fly. This means that the volumes pumped are not limited by mix tank capacities and the risk of
contamination is low.
<strong>The</strong> major components of most spacers are a viscosifying agent and a weighting agent (e.g. barite, calcium
carbonate, etc.). Small concentrations of other materials such as drilling fluid thinners and fluid loss additives may