Excessive water production can detrimentally affect the profitability of hydrocarbon-producing wells if not controlled properly. Water cut present in the oil stream from wells producing in several offshore Mexico fields is an issue of critical importance because oil production is sent to exportation. Lack of water handling facilities forces operators to monitor wells with water cut as low as 2.0%. Water production is normally controlled by decreasing the choke size, but in the worst cases can require shutting the well in completely, causing a negative impact on the production of the fields. Two main drivers of excessive water production in these mature fields are the influx of water behind the casing and/or water flowing through the natural fractures of these carbonate reservoirs. This paper describes the successful field implementation of a selective hydrocarbon-based ultrafine cement (UFC) slurry system to slow down water production in offshore Mexico.The UFC slurry consists of ultrafine cement with an average particle size of 2.5 µm, a surfactant, and a hydrocarbon carrier fluid (i.e., diesel). Because the slurry is hydrocarbon-based, it remains inactive when contacting an oil-producing zone. When the system contacts a water producing zone, the slurry will remain pumpable for an additional 20 to 30 min before beginning to set. The delayed setting of the cement slurry is ideal for placing the UFC slurry into water-bearing formation fractures some distance away from the wellbore. The slurry is designed to selectively shut off water flowing into the wellbore and is applicable up to 204°C. This paper describes the field implementation of the UFC slurry system in offshore Mexico to seal off unwanted water flowing through natural fractures and/or behind the casing. A variety of case histories are discussed in detail along with postproduction numbers after the treatment. Numerous UFC treatments have been performed in southern Mexico. 2

Sand production is a problem that plagues many reservoirs and has strongly affected benefit-cost relationships in the oil industry for years. Research dating as far back as the early 1930s has documented sand-production problems in unconsolidated formations.These problems are not related to one specific location or area, and although sand production is a worldwide problem, the major documented areas of sand production are in the USA, Canada, the North Sea, Europe, Venezuela, Bolivia, Brazil, and Colombia. Major causes of sand production include depletion, a change in flowing fluids, a change in stresses, and wellborestability failure.Failure to manage sand production can have a significant impact on the productivity of the well with the possibility of causing an eventual well collapse.In this paper, the application of a numerical simulator used for sand prediction in a gas well is presented. The simulator predicts the amount of produced sand and its effect on the productivity of the well. The model is based on the hydro-erosion model, first proposed by Vardoulakis in 1996(Vardoulakis et al. 1996. The model is based on rigid, porous media (no skeleton deformation), in which mass balance is applied to a three-constituent system comprised of solid, fluid, and fluidized solid using the homogenization-mixture theory. Subsequently, Wan and Wang (2002) extended this pure-erosion model to include the effects of the deformation of porous media in a consistent manner. A single-phase flow is iteratively coupled with geomechanics within a continuum mechanics framework. Furthermore, Wang (2004) extended previous work to develop a fully coupled reservoir-geomechanics model to account for the effects of multiphase flow and geomechanics in a consistent manner.By using this numerical simulator application, the severity and quantification of the problem of sand production were resolved, resulting in an acceptable economical return. The results of this field case are documented below in further detail. The Sand-Production ProcessSand production occurs when the stresses of the formation exceed the strength of the formation. The formation strength is derived from the natural cementing material that bonds the sand grains together. Sand grains are also held together by the cohesive forces caused by the immobile formation water.The stress of the formation-sand grains is caused by many factors, such as tectonic actions, overburden pressure, pore pressure, stress changes from drilling, and the drag forces of the producing fluids.Sand production is rate-sensitive in that there is a rate below which no sand production occurs. This reduced producing rate can be uneconomical because some formation sands might be produced with a fairly low fluid velocity. In some unconsolidated sands, the cementing agent is clay and mud that forms a weak material that provides little or no strength to withstand the formation stresses. In such a case, a wellbore might produce sand even during the production tests. Other formations might initially produce sand-f...

To execute the drilling well plan in Cantarell field, located in the Gulf of Mexico, Petroleos Mexicanos (PEMEX) is implementing a methodology to get a better control during the drilling stage. This methodology uses the conventional available information and a new pressure profile 3D Model. This model has been generated from available information, such as: logs, geologic/geophysics information, pressure values, and drilling mud weight. The methodology is being implemented and adjusted successfully as follow: construction of new wells by recommending casing setting depth after an abnormal pressure zone, determining an operational window for drilling fluids, identification of transitional pressure zones, analysis of the expected dynamic pressures, and recognition of zones with potential torque and drag problems. Introduction The prospect generation and production maintenance plans of Cantarell, the largest offshore production field in the world located in the south part of the Gulf of Mexico, need a better performance in well construction stage compared to the current operational status. For this reason, a multidisciplinary working team is implementing a different approach in the drilling planning process that uses a new Pressure Profile 3D Model. To complete a single well, three drilling phases are required: surface, intermediate, and production. Drilling operations during construction of the intermediate hole have to deal with the following conditions: presence of an abnormal pressure zone from Miocene-Oligocene to Eocene, critical casing setting depth just after this abnormal pressure zone has been left and a subnormal pressure zone appears, total and partial lost circulation in Eocene-Paleocene, hydraulic performance, and lost circulation during cementing jobs. The pressure profile 3D model was obtained processing logs in conjunction with data from vertical or nearly vertical wells distributed over the field; for instance, resistivity, travel time, density, neutron-porosity, and gamma-ray response. Pore pressure and fracture gradient for these wells were estimated using the most common methods and also innovative methods, then the 3D Model was generated with additional information such as: the most accurate horizons, formation tops, stacking velocities, and local structural geology. Model calibration was done considering drilling events, drilling fluids density, and static measured pressures. The main applications of the 3D Model here described are the following: starting point to recommend casing setting depth for the critical stage, establishing an operational window for the drilling fluids, recognition of the transitional formation pressure zones, analysis of the expected dynamic pressures during drilling and casing cementing, and recognition of zones with potential torque and drag problems. It is being showed that using this methodology, this 3D Model in combination with conventional available information works in a more effective way than usual because the working team has a systematic and effective control in all the monitored parameters. Area of interest Location The Cantarell and Sihil fields are located in the Gulf of Mexico approximately 80 Km Northwest from Ciudad del Carmen, Mexico, on a 120 Km[2] area with approximately 60 meters of water depth. The Cantarell field produces out of five blocks: Akal, Nohoch, Kutz, Chac and Sihil. The oil industry development has focused in the allocthonous Akal block because of its great dimension, but the new drilling plan is giving some importance to recently discovered Sihil field in the autochthonous block.

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