In this paper, we present a water-cut estimator utilizing the function approximation capability of an artificial neural network (ANN). The inputs to the ANN are optical sensor readings in a Red-Eye water-cut meter, which features the near-infrared (NIR) absorption spectroscopy technology. The initial training of the ANNwas done with a data set acquired from our multiphase flow-loop test facility, which was filled with live oil, water and gas. The test fluid stream was adjusted with good ranges of water-cut and gas-volume fractions which were supposed to cover the situations that can be foreseen in real production. However, clear discrepancies between the outputs of the ANN and the water-cut values from BS&W measurmentswere observedwhen the ANN was applied to actual production data measured by Red-Eye meters installed at two offshore wells. To address this issue and equip the ANN with self-adapting capability in real application, we propose a Bayesian approach to update the parameters of the ANN based on both initial flow-loop data and collected field data. The performance of the adapted ANN on both the data sets shows the effectiveness of the method.
Figure 1 shows the type of production response that is possible when applying a polymer gel treatment to a waterflood injection well to improve sweep efficiency. The figure shows the combined production-response of the four direct offsetting production wells to the gel-treated injection well. The gel treatment was applied for waterflood sweep-improvement purposes to the naturally fractured Embar carbonate formation surrounding Well O-7 of the highly mature SOB field in the Big Horn basin of Wyoming. The wide variations in water/oil ratio (WOR) and oil production rate are quite common in many of the well patterns of this highly fractured reservoir. Sydansk provides more details regarding the 20,000 bbl gel treatment.
This includes, during water- or gas-shutoff treatments, identifying the flow path of excessive water or gas production from its source to the production wellbore. The following procedure for gel technology selection is highly generalized, and the procedure should be modified as dictated by the actual reservoir conformance problem to be treated. If a service company or a company specializing in conformance treatment gels is to be involved, they should be consulted during each step of the selection process. A prerequisite is to eliminate all gel technologies, if any, that are prohibited by locally applicable safety or environmental regulations. First, determine the type of problem that is to be treated. That is, whether it is a matrix-rock problem or a high permeability anomaly problem, such as fractures. If treating a matrix-rock problem, decide if you need a gel for treating near-wellbore or deeply in the reservoir.
Proper placement of conformance improvement gels is key to achieving the desired results within the reservoir. The flow properties of a gelant or gel as it is being placed are important parameters. To date, for all known gelant solutions used in conformance improvement treatments (including polymer gelant solutions), these gelant solutions place themselves in all matrix-rock geological strata according to Darcy flow considerations and do so without any special selective placement in only the high-permeability strata and flow paths. Any placement of gel into, and the associated permeability reduction of, a low-permeability and/or high oil saturation strata in the near-wellbore region surrounding a radial-flow matrix-rock-reservoir well will almost always be counter productive to improving the conformance of that well. Thus, when applying a gel treatment, especially a near-wellbore gel treatment, to treat a vertical conformance problem of a radial-flow well in a matrix rock reservoir, mechanical zone isolation must be used to assure that the gelant is injected only into the high-permeability and/or low-oil-saturation geological strata to be treated.
Conformance is a measure of the uniformity of the flood front of the injected drive fluid during an oil recovery flooding operation and the uniformity vertically and areally of the flood front as it is being propagated through an oil reservoir. The remediation, or partial remediation, of the first conformance problem is exemplified by a mobility-control polymer flood conducted in a reservoir containing a viscous oil and/or a reservoir that is characterized as being relatively homogeneous. Successful conformance improvement treatment is dependent on correctly assessing the nature of the conformance issue. Vertical conformance problems, which are probably the most pervasive and most easily remedied conformance problems in matrix-rock (unfractured) reservoirs, are commonly manifested by geological strata of differing permeability overlying one another. In matrix-rock (unfractured) reservoirs, areal conformance problems, also referred to as "directional" high-permeability trends, can exist.
This article describes the chemical make-up and application of the types of gels most commonly used in conformance improvement. Oilfield conformance improvement gels come in a wide range of forms and chemistries. Table 1 provides an overview of various conformance improvement gels. CC/AP gels have an exceptionally robust gel chemistry and are highly insensitive to oilfield and reservoir interferences and environments. They are also applicable over an exceptionally broad pH range. As a result, these gels, when properly formulated, are applicable to the acidic conditions associated with CO2 flooding for which most earlier oilfield polymer gels did not function well.
The term "resin," as used in this page, refers to an organic, polymer-based, solid plastic material. Oilfield resins are exceptionally strong materials for use in blocking and plugging fluid flow in the wellbore and/or the very near-wellbore region. The three classical oilfield resins discussed here have exceptionally good compressive strengths. Also, these three resins usually have good bonding strength to oil-free rock surfaces. Resins for fluid-shutoff purposes during squeeze treatments can normally only be placed in the wellbore, perforations, gravel packs, or other near-wellbore multi-Darcy flow channels.
Early application of polymers for use during oilfield conformance improvement operations was focused on improving volumetric sweep efficiency of waterfloods. More recently, polymers have been used extensively in disproportionate permeability reduction (DPR) and relative permeability modification (RPM) treatments for water shutoff and in conformance improvement polymer-gel treatments. This page discusses polymers used in oilfield operations and how they contribute to conformance improvement. Polymers are large molecules and chemical entities referred to as macromolecules. Polymer molecules are the resultant chemical specie when a large number of relatively small and repeating molecular entities, called monomers, are joined together chemically.