In the Bay of Campeche, Mexico Marine operators have recently commenced the development of their high pressure, high temperature (HPHT) oil and gas fields in order to meet the high demand. These new developments present tough conditions for all aspects of well drilling and completion activities. They are particularly challenging for performing well intervention, which have driven operators, manufacturing and service companies to develop innovative strategies for servicing these fields. For HPHT well developments, electric line conveyed guns is the most common technique employed to perforate wells in the area, whether dynamic or static conditions. Nevertheless, coiled tubing (CT) deployed perforating has been recently employed as a reliable option in the following cases:Electric line is not a technically suitable option due to the limited magnitude of under-balance at which it can safely operate.Drag and buoyancy forces encountered in the wellbore are close to the operational limits of the cable.Wellbore tortuosity, tubular restrictions and well configuration render electric line unable to access perforation target depth. Initially, this paper discusses the workflow for performing technical analysis to develop safe and economical CT conveyed perforating operations for HPHT wells in offshore Mexico, which considers CT string design, surface equipment, well control equipment and associated downhole tools. It then presents case histories and lessons learned. And finally, provides conclusions and recommendations from the experiences gained for performing HPHT CT deployed perforating activities in Mexico Marine. Introduction HPHT define well conditions above what is considered normal levels of pressure and temperature. For Mexico Marine operators any well intervention with wellhead pressure (WHP) above 3,500 psi and bottomhole temperature over 150 oC (BHT) is considered HPHT. The Bay of Campeche is located at the southeast of Mexico in the continental platform of the Gulf of Mexico in front of Tabasco, Campeche and Yucatan coasts (Fig. 1). In 2004 Mexico Marine operators started to develop in the Bay of Campeche a significant number of fields that meet HPHT definition. In Mexico Marine HPHT fields, electric line conveyed gun is the most common technique employed to perforate wells. However, CT conveyed perforating has been recently proved as an excellent option in cases where electric line restricts under-balance magnitude for safe operation, drag and buoyancy forces encountered in the wellbore are close to the operational limits of the cable, and tubular restrictions and well configurations may be a concern to access perforation target depth. Mexico Marine HPHT Environment HPHT developments (Fig. 2) in the Bay of Campeche target Cretaceous (K) and Upper Jurassic Kimmeridgian (UJK) formations. Cretaceous is a naturally fractured carbonate formation ranging depths from 4,500 to 5,500 m with Porosity ranges from 3.0 to 5.0% and Permeability of 18 md. Upper Jurassic Kimmeridgian is a dolomitized carbonate formation in Oolitic banks from 5,000 to 6,000 m, where Porosity ranges 5.0 to 8.0% with Permeability from 20 to 40 md. The new fields under development are highly pressurized with bottomhole pressure (BHP) from 10,000 to 12,000 psi and BHT up to 190 oC. In surface, shut-in pressures from 6,000 to 8,500 psi have been recorded, and hydrocarbon production is composed by gas and oil from 27.0 to 48.0 oAPI. Drilling operations are performed by jackup rigs from eight-leg fixed platforms in water depths up to 60 m. Well deviation ranges 0 to 60 o, and jackup rigs are also the most common structures available for well completion and workover operations. These rigs have a limited crane capacity of 30 ton to lift and position CT string onboard.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSeveral different hydraulic fracturing treatment design methodologies have been adopted and used with varying success in East Texas and, specifically, in the Cotton Valley Sand Formation. Treatment designs have ranged from massive hydraulic fractures using crosslinked polymer fluids to low proppant concentration slickwater treatments (waterfracs) using only water plus a friction reducer. Operators have varying opinions regarding the benefits of the various design approaches, with the only common conclusion being that hydraulic fracturing must be employed to commercially produce hydrocarbons from these tight formations. The major design challenges include the need for long fractures, relatively limited height growth, good proppant coverage over the entire fracture surface, and low proppant pack damage. Neither conventional fracturing treatments nor slickwater fracturing treatments address all of these issues.To meet the challenging design requirements, a new design methodology in which fibers are added to the fracturing fluid has resulted in added benefits for operators. The fibers assist in the transport of proppant based on a mechanical suspension mechanism and prevent proppant settling during fracture closure. As a result, the fluid viscosity is no longer the main factor in proppant transport and significantly lower polymer concentrations can be used without compromising proppant transport. For example, the polymer concentration used in several successful treatments at BHST in excess of 250 o F has been reduced by about 50% when used in conjunction with the fibers. The lower fluid viscosity allows for the creation of the desired fracture geometry with controlled fracture height growth. In addition, reducing the polymer concentration has largely been accepted as a means to increase fracture conductivity. The use of fibers in conjunction with the polymer fluid is a new approach that has allowed for additional reduction in polymer loadings while still maintaining excellent proppant transport in over 90 jobs pumped to date.The purpose of this paper is to share the fracture design methodology incorporated for several operators completing wells in East Texas. Typical job designs with fluid rheology and laboratory conductivity data are presented in conjunction with the placement success when using the fiber assisted transport design methodology. Initial production results are reviewed and compared to offset wells that have been stimulated using conventional methods.
fax 01-972-952-9435. AbstractIn the Bay of Campeche, Mexico Marine operators have recently commenced the development of their high pressure, high temperature (HPHT) oil and gas fields in order to meet the high demand. These new developments present tough conditions for all aspects of well drilling and completion activities. They are particularly challenging for performing well intervention, which have driven operators, manufacturing and service companies to develop innovative strategies for servicing these fields.For HPHT well developments, electric line conveyed guns is the most common technique employed to perforate wells in the area, whether dynamic or static conditions. Nevertheless, coiled tubing (CT) deployed perforating has been recently employed as a reliable option in the following cases: • Electric line is not a technically suitable option due to the limited magnitude of under-balance at which it can safely operate. • Drag and buoyancy forces encountered in the wellbore are close to the operational limits of the cable. • Wellbore tortuosity, tubular restrictions and well configuration render electric line unable to access perforation target depth. Initially, this paper discusses the workflow for performing technical analysis to develop safe and economical CT conveyed perforating operations for HPHT wells in offshore Mexico, which considers CT string design, surface equipment, well control equipment and associated downhole tools. It then presents case histories and lessons learned. And finally, provides conclusions and recommendations from the experiences gained for performing HPHT CT deployed perforating activities in Mexico Marine.
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