Setting and hardening of hydraulic cements
Setting and hardening of hydraulic cements
In August 2004, Adriatic IV was on location over the Temsah gas production platform, off Port Said, Egypt in the Mediterranean. During the drilling of natural gas well by rig, a gas blowout occurred during the drilling operation. Due to this blowout, the whole Petrobel platform was burnet out. This platform was owned jointly by BP, Italy’s ENI and Egypt’s General Petroleum Corporation was damaged beyond repair and Egypt’s petroleum minister ordered its destruction. An engineering firm Tacon designed the platform. Tecon developed the basic structural design along with offshore structure SASP, of the platform jacket for Petrobel Egypt.
Tecon was responsible to perform the foundation design and all naval and installation analysis. Tacon also developed all A. F. C. structural drawings. [Tecon] The blowout on the offshore of the platform was the consequence of annular flow after cementing using spooled wellheads. Following part of case study shows why blowout occurred with all analysis. TEMSAH: Temsah is a gas production platform owned jointly by BP, Italy’s ENI and Egypt’s General Petroleum Corporation located in the off port said, Mediterranean Sea. On 10th August 2004, the Adriatic IV was working as usual on the Temsah platform.
The rig was drilling natural gas well when a blowout occurred during the drilling operations. Reports and various other sources stated that there was an explosion followed by fire, which was initially contained on the jack-up. [JWC] The fire then spread to the Petrobel-run platform where it continued to rage for over a week before being brought under control. There were more than 150 workers on the jack-up as well as on the platform. All the workers on the jack-up and platform were evacuated with no casualties, due in part to the prior recommendation that production activities be ceased as a precautionary measure.
The firefighters battled for almost a week to control the fire burning on a rig pumping natural gas out of the Mediterranean Sea as reported by Egypt’s semiofficial news agency. Oil Ministry officials, speaking on condition of anonymity, told the Middle East News Agency (MENA) that workers were drilling holes in a leaking well to release gases to contain the fire, while firefighters are dousing the platform with seawater. [JWC] It took almost a week to control over the fire. According to the, Global Santa Fe, Adriatic IV was sunk and not salvageable.
The platform, owned jointly by BP, Italy’s ENI and Egypt’s General Petroleum Corporation was damaged beyond repair and Egypt’s petroleum minister ordered its destruction. Almost one year after this accident, the Temsah was fully repaired and production at Temsah field started in a full-fledged manner. It was back on stream at full production rates. 2. Cement types and cementing structure The above blowout caused due to the cementing structure and method. Discussed here is the cementing process that probably caused the blowout.
“After running 9 5/8″ Casing to 2754 meters, performing a cement job, waiting on cement for 14 hours, and setting the casing slips, the well started to flow from the 9 5/8″ by 13 3/8” annulus, while installing the primary packing (sealing element). The flow consisted of salthingyer and gas. The wells on the Temsah NW platform were shut in and the gas lines to and from the platform were depressurized. Thus the wells on the W. Akhen platform were shut in, as the gas, production lines go through the Temsah NW platform. On-essential personnel were evacuated from the rig. Nipped up the BOP and space out riser. Shut in pressures were 1480 psi.
Shortly thereafter the flange between the wellhead B section and the riser below the BOPs started leaking salthingyer and gas. Since the initial incident, the flow had continued through the leaking flange and increased. Remedial efforts to date had not been successful in containing or controlling this flow. When cement casing is done in the well, Blowout Preventers are usually picked up to set the slips on the casing to hold it in place. Due to this, well is open to the world. Cement is counted on to hold any gas down hole, but if the cement is lighter than the bottom whole pressure, the well will come in.
The way to avoid this is to wait longer on the cement to set and monitor any gas migration to surface. This process was not done, which would have probably prevented the blowout on the platform. Facilities for placing cement: Wellheads are nothing but the end connection to concentric well casings, which are cemented into the ground. The critical purpose of this wellhead is to provide a base onto which safety equipments (blow-out preventers) is installed throughout the drilling phase of a well and to which production flow control equipment is attached, before a well can safely put into the production.
To confine the downhole pressure to the smallest inner casing and eventually the production tubing, wellheads contain annular seals, which serve to isolate the last casing into the high pressure resistant wellhead housing body. [UNEP] Type of cement: The type of cement used in the well was Hydraulic cement. Hydraulic cements are materials that set and harden after being mixed with water, because of the chemical reactions with the mixing water.
After hardening, the Hydraulic cements retain strength and stability even under water. The key requirement for this strength and stability is that the hydrates formed on immediate reaction with water be essentially insoluble in water. Most construction cements today are hydraulic, and most of these are based on Portland cement, which is made primarily from limestone, certain clay minerals, and gypsum in a high temperature process that drives off carbon dioxide and chemically combines the primary ingredients into new compounds.
Setting and hardening of hydraulic cements is caused by the formation of water-containing compounds, which are formed as the result of reactions between cement components and water. The reaction and the reaction products are referred to as hydration and hydrates or hydrate phases, respectively. As a result of the immediate start of the reactions, a stiffening can be observed which is initially slight but which increases with time. The point at which the stiffening reaches a certain level is referred to as the start of setting.
Further consolidation is called setting, after which the phase of hardening begins. The compressive strength of the material then grows steadily, over a period that ranges from a few days in the case of “ultra-rapid-hardening” cements to several years in the case of ordinary cements. Non-hydraulic cements include such materials as (non-hydraulic) lime and gypsum plasters, which must be kept dry in order to gain strength, and oxychloride cements, which have liquid components.
Lime mortars, for example, “set” only by drying out, and gain strength only very slowly by absorption of carbon dioxide from the atmosphere to re-form calcium carbonate through carbonatation. [Wikipedia] 3. Time scale The time scale for the cement specifies the amount of time in years the cement will provide the strength to the structure. Time scale of cement structure truly determines the quality of the cement structure. Time scale for the cement structures must be longest it can be. The time scale for the Egypt Temsah was more than hundreds of years.
It was a building structure into the Mediterranean Sea with very strong and rigid foundation. Mediterranean sea, Port Said, well of Temsah was built with concrete materials. Wellheads were also made with the same kind of cement materials. [UNEP] Cement Success: Cement success is nothing but the successful completion of a cement structure in the various testing methods. Cement is assumed to be successful when any benchmark for the structure is completed. For-example in Egypt Temsah the platform was destroyed after many decades. This total age or decade specifies the cement success.