RIASSUNTO
Abstract
The Chuc-A production platform produced an average of 59,200 BPD until October 24th 1997, in this date a fire happened when installing a separator. This oil volume corresponds to the 43% of the field total production. Once the fire was controlled, the personnel of the Drilling Management and Wells Maintenance proceeded to inspect the area with propose to prepare a plan to control wells.
In this paper the operative program and the developed activities to mend wells are shown, incorporating them to production. The activities have been divided in three stages: a) wells control after damage and change of valves to the production trees damaged by fire, leaving them in safe conditions, b) control of wells for the Chuc-A platform restoration and c) Tubing recovery, cut and change of wellheads and production trees, tubing pipe introduction and new subsuperficial safety valves (SSV), stimulation, production surveys, and beginning of the production. Besides, a list of materials, services, safety equipment, logistic and human resources is included which are necessary for the wells recovery.
To carry out the repair operations of all the wells, a total of 387 days was necessary, with a total cost of 15.7 MMUSD, being the rent of equipment the biggest percentage equal to 54.8%. The costs related to services were equal to 4.6 MMUSD, and the costs of materials reached to 2.5 MMUSD. At the end of the operations the eight flowing wells were incorporated to production with similar flow rates to the original ones.
Between the first and the second stage, the wells were set in production during six months while the necessary materials and services were acquired for the final repair of wells.
Introduction
The Chuc field is located approximately to 70.2 marine miles (130 Km) to the Northeast of the Marine Terminal of Dos Bocas, Tabasco, Mexico, in the area named light oil, figure No. 1. This field was discovered in September 1982 with the drilling of the Chuc-1 well, the well was flowing light oil of 31° API in the lower cretaceous formation with an average flow rate of 7500 BPD and a bottomhole pressure of 5675 psi.
The Chuc geological structure is defined by an anticlinal trap with NE-SW orientation connected with an aquifer that is located to the deep of 4014 m (13,166 ft TVD) under sea level. One important feature of the field is the presence of salt intrusion, which has the same structure orientation and divides the field in two blocks, west and east.
The production mechanism has a relation with the expansion of the fluid-rock system and a regular inlet of water. Now the reservoir is exploited together with the Abkatun and Pol fields by means of the secondary recovery system (water injection) which its purpose is to keep pressure in the fields.
The field hydrocarbons are found in the carbonate formations, being the named ""paleobreccia-upper cretaceous"" the most important of them. Up to date twenty eight wells have been drilled, thirteen of them are producers, nine of them are closed temporarily, five are plugged, and one is considered as an observation well.
On October 24th 1997, during the installation of a separator with a capacity of 150,000 BPD, an oil and gas leak was observed and later a fire of great importance which was controlled the same day. The field productions before the disaster of the Chuc-A platform was about 137,000 BPD and the mean pressure about 3925 psi.
1. Wells Control After Damage
Once the fire was controlled, the wells area was inspected to determine the condition of the wellheads, Christmas trees, superficial lines and production pipes, from this inspection it was observed that the most exposed wells to fire were the 4, 31, 16-A, 34-A, 14, 14-A, 201, y 22. See figure 2.
A multidisciplinary group was formed immediately which analysed the different alternatives that could be presented in each well to determine the necessary tools and materials, obtaining the flow diagram shown in figure 3.