Waterflood recoveries from certain areas in this large, thick carbonate reservoir were below expectations. An integrated (geological, petrophy:ical, and engineering) study was undertaken to (1) develop a geological-petrophysical model covering the areas of interest, (2) evaluate past reservoir performance, (3) predict future performance for various operating plans, and (4) make appropriate recommendations based upon technical and economic considerations. It was concluded that low oil recovery resulted primarily from low to very low formation permeabilities, injected water channeling because of fracture treatments administered during primary production, net pay intervals still behind pipe (mainly in producers), and limited control of injection/production well profiles. Results of the study indicated that oil recovery could be increased significantly by infill drilling/waterflood expansion.However, the most attractive plan from an economic viewpoint was to open the unperforated net intervals in existing producers and injectors and to monitor/improve flow profiles. Other enhanced recovery methods were not attractive because of either low permeability or low oil gravity.

An excessive water cut or high gas/oil ratio in a production interval presents a major concern in sustaining oil production, often requiring fast and efficient workover solutions to enhance the oil recovery process. Wells in the Cantarell field, a mature depleted field in the Bay of Campeche in the Gulf of Mexico, are facing drastic decreases in their production and, depending on producing zone, an increase in either water cut or gas/oil ratio. Other developed fields in Mexico's Region Marina, such as the Ku-Maloob-Zaap, have constantly increased their hydrocarbon production through the years with an incipient increase in water and gas increments.The high water cut and gas increments have had a strong impact on the production strategy, opening the opportunity for application of non-conventional, innovative, and engineered solutions to isolate or abandon production intervals invaded by gas or water and continue production from upper or deeper zones. The pay zones consist of naturally fractured, vugular carbonates with permeability as high as 5 Darcies, from Paleocene, Cretaceous, and Jurassic formations. Their characteristics present the following challenges that need to be overcome to succesfully achieve the required isolation: Loss of fluid circulation, which is necessary for well control and also negatively affects the fluid placement in the workover jobs.  High gas presence, gas cap driven, which is a major concern on surface.  Lack of primary zonal isolation, resulting in migration of water or gas to the productive intervals. This paper summarizes the non-conventional technologies and techniques applied to isolate the water and gas producing intervals and their synergistic performance: reticulated gel, lost circulation fiber tecnologies and gastight slurries integrated in an engineered solution. Results from field cases demonstrate the design, execution, and evaluation of these applications.

In exploration wells in shallow waters of Mexico, the challenge of reducing drilling time and enhancing efficiency of well construction had become a problem on a daily basis. The continued use and success of Casing while Drilling (CwD) led the operator and service companies to embark upon a more ambitious project. Using the learning curve of previous 20″ CwD conductor sections, the first 34″ PDC drillable drill bit was designed and the first Casing Running Tool (CRT) for 30″ casing was utilized. These tools were used to apply the technology in the conductor sections of wells targeting Mesozoic formations. A technical feasibility study was performed by the operator and service companies involved to analyze the viability of executing this whilst creating new products. This saw the implementation of CwD using 30″ casing, an integral drilling system using casing as the drill string and a PDC drillable bit that allows drilling and casing of the section to take place simultaneously and eliminates the need to assemble a 36″ drilling BHA and, subsequently run casing. Once the CwD BHA (Casing + Drillable drill bit) reaches the final depth of the section, the hole is already cased and ready to cement. This challenged the service companies' engineering departments to develop the custom made tools for the application. In the first well, the original plan was to drill the 30″ section using a 36″ roller cone bit, drilling from sea bed (+/-78m) to 250 mts. This was the candidate well that the operator chose to utilize an ″unconventional″ drilling system to ensure reaching TD in a single run prior to cementing the casing. The 30″ × 34″ conductor section was drilled and cased at a depth of 256 meters, drilling a total of 178 meters with the PDC drillable drill bit (4 blades + 19 mm cutters) in 9:52 hrs., with an average rate of penetration (ROP) of 18.04 m/hr., and then preparations for cementing the 30″casing began. This entire operation represented a 26.3% time reduction compared with a conventional drilling operation This document will show the methodology and technology used in Mexico Marine Exploratory fields to reduce and mitigate the risk of not setting the casing at TD, focusing on the pre-planning stage, proper bit selection, Torque & Drag (T&D) analysis, casing fatigue life analysis and the use of new technology with a high success ratio on the operations in order to add value and ensure the customer' satisfaction.

Since its initial discovery in 1975, Offshore Mexico has been the most important oil producing region in the country, with production peaking at 2.8 MBOPD in 2003. However, since 2004, production has been quickly dropping and showing signs of field maturity; current production rate is at 1.8 MBOPD. Coiled tubing (CT) intervention had been typically required to keep production rates steady or even achieve improvement. In 2003, the operator and CT service provider formed a joint venture to put efforts to enable innovative solutions for addressing the challenges of this region. The document discusses the various industry drivers that necessitated service improvements and technology introductions for successful CT well intervention over the last ten years. This paper focuses on the following areas: Drilling and workover environment: Extension of CT interventions in low-pressures to high-pressure wells (self imposed maximum potential wellhead pressures above 3,500-psi) Expansion of Offshore rigless interventions (from conventional operations on fixed platforms to boat-based operations) Extension of CT interventions from fixed-deck to deepwater floater operations CT Applications Conformance applications for water shut-offs and subsequent new perforations Logging interventions in long horizontal sections Real time downhole measurements during well interventions with CT equipped with fiber optic telemetry systems replacing downhole memory gauges CT Equipment Improvements Surface equipment improvements from conventional CT equipment to "latest generation" automated CT unit with active process control and safety systems In summary, this paper presents an overview of the past, a review of the present and discussion of the anticipated future of CT services in the Offshore Mexico region in the context of short, medium and long term technical challenges are presented in several case studies.

No abstract