INSPECTION PROGRAM IMPROVES BULK CEMENT SYSTEM DELIVERY

Terry O'Bannion Halliburton Energy Services Houston Bart Guidroz, Glen Morris Halliburton Pneumatic Systems New Orleans A recently implemented survey of pneumatically operated bulk cement-handling equipment offshore has improved bulk cement deliverability on several Gulf of Mexico rigs. The 30-point survey helps ensure an adequate rate of bulk cement delivery throughout the cement job.

Dec. 20, 1993

4 min read

Terry O'Bannion
Halliburton Energy Services
Houston

Bart Guidroz, Glen Morris
Halliburton Pneumatic Systems
New Orleans

A recently implemented survey of pneumatically operated bulk cement-handling equipment offshore has improved bulk cement deliverability on several Gulf of Mexico rigs.

The 30-point survey helps ensure an adequate rate of bulk cement delivery throughout the cement job.

The inspection survey was developed because the source of many cement job failures was a lack of adequate, steady delivery of bulk cement to the cementing unit during the job. The job failures caused by flow interruptions, plugging of tools by chunks of set cement, and erratic flow resulted in poor primary cement jobs, many of which required remedial cementing jobs. A better-controlled flow of cement may help prevent these types of failure, thereby reducing the number of remedial cement operations.

The use of recirculating cement units equipped with automatic density control systems has drawn attention to pneumatic bulk supply systems. The automatic density control system puts out a post-job record showing cement density throughout the job; there is no doubt as to when flow has been interrupted or becomes erratic.

On rigs having a history of erratic cement delivery, pressurized separator tanks are often included in bulk delivery systems to provide a steady flow of dry cement. A nonpressurized version of the separator can be used to feed (by gravity) a cement hopper for jet mixing systems.

Implementation of the survey requires a close working relationship between the drilling contractor and the cementing service company. The program features a follow-up survey by inspection personnel after 120 days and quarterly reviews by the contracting company tool pusher and the service company cementer as long as the rig is operational. Each rig receives a formal survey (like the original) every 1-1/2 years.

The service company strategy in offering the inspection service is to help eliminate most problem jobs caused by faulty bulk delivery systems in the offshore rig fleet. To date, 44 Gulf of Mexico rigs have been inspected, and enough personnel are being trained to allow expansion of the program worldwide. Training, inspection reports, and records are uniform worldwide. Thus, a rig could move from the Gulf of Mexico to the North Sea, for example, and still retain the integrity of its inspection program.

The program also applies to inspection of pneumatic systems for delivering dry drilling mud materials.

SURVEY PROGRAM

The pneumatic survey program is pro-active; the survey teams are not brought in to evaluate Systems only because of problem jobs. The survey team deals only with the rig contractor to improve the bulk delivery performance. The results of inspections are not shown to or discussed with the production company client.

The accompanying box summarizes the procedures followed in surveying the fitness of each system. Fig. 1 is a schematic of a typical offshore pneumatic system cement bulk tank, illustrating points of inspection and other pertinent data. The tanks are tracked by serial number, and the survey results are listed at the bottom of each schematic.

A similar check sheet is made up for rig air compressor inspection. An inspection sheet is completed and furnished to the contractor for each tank and compressor on the rig.

The jet assembly is another important element of bulk-handling systems; the assembly is inspected for buildup of material on the inner walls (Fig. 2).

A special software program analyzes bulk systems that are not delivering as expected, even after corrective actions have been taken. The software is also used in planning a new bulk delivery system.

The program requires the following input data:

Air compressor capacity (in cu ft/min)
Air compressor working pressure
Inside diameter of conveyor pipe
Material used (cement, drilling mud)
Geometry of conveyor pipe routing (horizontal distance, vertical distance, and turns or bends in the routing).

The program output indicates if the system "will" or "will not" deliver bulk material. If the system will operate, the program output includes the following:

System minimum and maximum velocities
The velocity at which solids fall out of the air/solid mixture.

Using program results, the analyst may detect and locate restrictions in the bulk system and recommend corrections. A typical impediment to good flow is the use of too many bends in the conveyor pipe routing.

FUTURE WORK

The bulk delivery-survey program also is being considered for the following applications:

Bulk supply vessels used by marine industry contractors
Remote plant locations, such as power companies, where pneumatically transferred materials are used
Training programs for operators and contractors
Maintenance program of bulk delivery systems.