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Results
Abstract Rapid production decline rate is associated with the loss of fracture conductivity after hydraulic fracture stimulation. This loss of conductivity has often been attributed to the migration of formation fines into the proppant pack or the generation of fines derived from proppant crushing. Surface modification agents were introduced in the stimulation market around 1997, and according to literature published since then, these materials have been helping to sustain fracture conductivity, and subsequently, mitigating production decline rates. This paper presents long-term results from the use of these materials in hydraulic fracture stimulation operations in the Burgos Basin in northern Mexico; results from offset wells are also presented for correlation and comparison. Production from this basin comes from low-permeability sandstones normally considered tight gas formations. Introduction Burgos Basin is located in northeastern Mexico along the southern border of the U.S. This gas basin covers more than 50,000 km2 (Fig. 1) and accounts for one third of the reserves of nonassociated gas in the country. The gas fields are located along well-defined bands that extend across the shared border between Mexico and the U.S. They are complex, sandy reservoirs, higly compartmentalized, and made up of a great number of small independent blocks characterized by very low permeability. Sustaining a high production level in this area requires a large number of wells to be drilled and hydraulically fractured.1 Burgos Basin gas production started in the mid-Forties; however, its complex characteristics caused a rapid decline by the early Nineties. In 1994, a second phase began when an intensive drilling program for exploration and development was kicked off with the goal of increasing gas production. New reserves were added by improving drilling and completion methods, identifying bypassed pay, identifying field extensions from 3D seismic information, and making new exploration discoveries. Fig. 1—Burgos Basin location in northern Mexico. Factors Affecting Fracture Conductivity Several factors affect the conductivity of a propped fracture and ultimately the productivity of a well. As mentioned, the migration of fines onto the proppant pack after a hydraulic treatment has been recognized as one of the main factors affecting fracture conductivity. This occurs when flocculation of the fines creates larger particles that result in a pack plugging. Infiltration of fines into a pack in effect reduces the conductive width of the fracture and provides a source of fines that may migrate upon stress cycling. Fines can be a product of the proppant breakdown under closure stress or they can come from the formation that is in contact with the proppant bed. Fines migration is often related to unconsolidated formations; however, it can also come from hard rocks if the fracture face crushes under the load of the proppant.2
- North America > Mexico > Tamaulipas (0.96)
- North America > Mexico > Nuevo León (0.86)
- North America > Mexico > Coahuila (0.86)
- North America > United States > Texas > Vicksburg Formation (0.99)
- North America > Mexico > Tamaulipas > Burgos Basin > Cuitlahuac Field (0.99)
- North America > Mexico > Nuevo Leon > Burgos Basin (0.99)
- (2 more...)
A New Method for Acid Stimulation without Increasing Water Production: Case Studies from Offshore Mexico
Hernandez Reza, Gabriel (Petroleos Mexicanos) | Soriano, J. Eduardo (Halliburton Energy Services Group) | Eoff, Larry S. (Halliburton Energy Services Group) | Dalrymple, Eldon Dwyann (Halliburton Energy Services Group)
Abstract Successful acid stimulation requires a method to distribute the acid between multiple hydrocarbon zones. Since almost all producing wells are inhomogeneous, containing sections of varying permeability, this can be a huge problem. In addition, the water saturation of the various zones plays an important role. Since acid is an aqueous fluid, it will tend to predominantly enter the zones with the highest water saturation. These water zones are also often the highest permeability zones, so acid stimulation will often result in large increases in water production. There are many negative aspects to increased water production, such as increased lifting and disposal costs, increased corrosion, etc. This paper describes the use of a new low viscosity system that inherently reduces formation permeability to water with little effect on hydrocarbon permeability, and also diverts acid from high permeability zones to lower permeability zones. This new system has been used in offshore Mexico in the Chuc, Caan, and Pol fields among others over the past year. During this time, over 30 wells have been treated with the new system. Most standard acid treatments in this field result in increased hydrocarbon and water production. The new system has resulted in increased hydrocarbon production with no increase in water production, and in some cases a decrease in water production. Details from several of these jobs will be presented showing the diversion and production results. Introduction In matrix-acidizing treatments, the acid tends to predominantly enter the highest-permeability layers and bypass the most damaged (lower-permeability) layers. In some cases, high-permeability layers are also predominantly water-bearing, thus acid also mainly enters those zones. In some cases, the acid may also break into a nearby water-bearing zone. In attempts to achieve uniform placement of acid across all layers, various placement techniques have been used. The most reliable method uses mechanical isolation devices (such as straddle packers) that allow injection into individual zones one at a time until the entire interval is treated. However, this technique is often not practical, cost-effective, or feasible. Without a packer, some type of diverting agent must be used. Typical diverting agents include ball sealers, degradable particulates, viscous fluids, and foams. Although these agents have been used successfully, all have potential disadvantages and none address the problem of increased water production that often follows acid treatments. Therefore, it would be a major advantage to have a material that could inherently decrease the formation permeability to water while also providing diversion. One method of controlling water production uses dilute polymer solutions to decrease the effective permeability to water more than to oil. These treatments may be referred to as relative permeability modifiers (RPM), disproportionate-permeability modifiers, or simply, bullhead treatments. The latter name is so called because these treatments can be bullheaded into the formation without the need for zonal isolation. RPM systems are thought to perform by adsorption onto the pore walls of the formation flow paths. A previous paper has described the development of an RPM based on a hydrophobically modified, water-soluble polymer (referred to here as an associative polymer, or AP). This group of polymers was selected for study because their properties can be altered in ways that render them valuable for oilfield applications. Another paper has described a laboratory study of this polymer for use as an acid diverter.
- North America > United States > Texas (0.47)
- North America > Mexico > Gulf of Mexico > Bay of Campeche (0.34)
- Asia > Middle East > Iran > Ilam > Zagros Basin > Day Field (0.99)
- North America > Mexico > Gulf of Mexico > Bay of Campeche > Sureste Basin > Campeche Basin > Abkatun-Pol-Chuc Field > Pol Field (0.94)
- North America > Mexico > Gulf of Mexico > Bay of Campeche > Sureste Basin > Campeche Basin > Abkatun-Pol-Chuc Field > Chuc Field (0.94)
- North America > Mexico > Gulf of Mexico > Bay of Campeche > Sureste Basin > Campeche Basin > Abkatun-Pol-Chuc Field > Caan Field (0.94)