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Collaborating Authors
Conformance improvement
Abstract The remaining oil in mature oilfields at high water cut stage is highly scattered in the whole field and relatively abundant in some localities. In view of this feature, a new approach is proposed to predict the distribution of the remaining oil in mature oilfields by integrating multidisciplinary means such as geology, seismic, geophysical well logging and reservoir simulation. At the high water cut stage, oilfields are always thin sand-shale interbedded layers and with numerous of wells, sophisticated target processing method of seismic data, sophisticated structure interpretation, combining of logging and seismic data in thin interbedded layers prediction and seismic constrained geology modeling technique are researched to construct the logging and seismic unit sophisticated reservoir characterization in mature oilfields. This technique has been applied in reprocessing old seismic data of Gangdong area in Dagang oilfield and improved the main frequency of seismic data by 10–15 Hz, and in X4–5 block in Xingshugang oilfield in Daqing with an average well distance of 200m, some new cognitions have been obtained in the faults, microtectonics and the distribution of the river channel sands in the block. With the result of combining logging and seismic prediction, high precision determinable reservoir model is established. Also the distribution of the remaining oil is predicted through large-scale sophisticated reservoir numerical simulation on the basis of this model. The case application shows that integrating multiple disciplines technique of predicting remaining oil in a mature oilfield with high water cut has a profound meaning for finding remaining oil effectively. Introduction Statistics show that more than 90% of China's oil reservoirs are composed of nonmarine clastic deposits and are seriously heterogeneous, characterized by complex pore structure, highly discontinuous sandbodies, multi-layered payzones with great difference in permeability, seriously faulted reservoirs with various geological characteristics, relatively high oil viscosity, and limited or even no natural energy supply from aquifer. After years of production, most oilfields in China have been at their mature stage with high water cut and high recovery. The remaining oil is highly scattered in general, but some locations with relatively abundant remaining oil still exist [1]. Therefore, it is of great significance to shift tasks of numerical simulation from study on field development strategy as in conventional cases to detailed study on remaining oil distribution in order to find those parts with relatively abundant remaining oil. Obviously, such study will place increasing demands on simulation speed, grid block number, grid technique, history matching technique, production flow technique among others and calls for the development of so called ‘sophisticated numerical simulation’ technique. In addition, tertiary recovery techniques such as polymer flooding, alkaline/surfactant/ polymer combination flooding can be used in a lot of oilfields in China to enhance oil recovery. Moreover, a lot of fractured sandstone reservoirs with low and extra-low permeability have been found, the development of which is more complicated. Therefore, numerical simulation demands for improved functions in such cases.
- North America > United States > Texas (0.49)
- Asia > China > Tianjin Province (0.34)
- Asia > China > Heilongjiang Province > Daqing (0.25)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.69)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.50)
- Geophysics > Seismic Surveying > Seismic Processing (0.48)
- Geophysics > Seismic Surveying > Seismic Interpretation (0.47)
- Asia > China > Tianjin > Bohai Basin > Huanghua Basin > Dagang Field (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Xingshugang Field (0.99)
- North America > United States > Louisiana > China Field (0.97)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Conformance improvement (1.00)
Abstract The main pay of Guantao Formation in Gudao Field is a large-scale thick positive-rhythm channel sand oil layer. At the extra high water-cut stage, the thick oil layer is waterflooded seriously, but the top remaining oil is still enrichment due to influence of reservoir heterogeneity. The research shows that the development effectiveness of tapping the potential with vertical well is bad and the economic benefit is low [1]. If horizontal well is used, the producing degree and the recovery of the remaining reserve can be improved effectively. Among various factors of affecting development effectiveness of horizontal well, the influence of intraformational bed development is much more important. The development of intraformational bed and its control on remaining oil distribution should be understood first, then the technology policy research of tapping the potential with horizontal well was conducted in order to ensure the good development effectiveness with horizontal well. In this paper, the remaining oil distribution features under the different developmental conditions of intraformational bed are expounded in detail, the intraformational bed was divided into two kinds, developed and undeveloped; according to its developmental conditions, the technology policies of horizontal well were studied respectively, and the commensurate design criteria of horizontal well was proposed. The application of the achievements in tapping the potential of remaining oil in thick positive-rhythm oil layer during the extra-high water cut period has achieved preferable effectiveness, which provides reference for that in the same type of reservoir. Key words Extra-high water cut reservoir, Thick positive rhythm oil layer, Intraformational bed, Remaining oil, Horizontal well Introduction Gudao oilfield is one of four uncompartmentalized oilfields in Shengli petroleum province, characterized by fluvial reservoir which is the primary type of reservoirs found in China [2]. At present, Gudao oilfield has been developed for more than 30 years and is at the extra high water cut stage, the distribution of remaining oil is very complicated due to the influence of reservoir heterogeneity and long-term waterflooding, and the challenge is how to tapping the potential of remaining oil at extra-high water cut stage. The main pay of Guantao Formation in Gudao Field is a large-scale thick positive-rhythm channel sand oil layer. At the extra-high water cut stage, the thick oil layer is waterflooded seriously, but the top remaining oil is still enrichment due to influence of reservoir heterogeneity. The research shows the problem existing in the thick positive rhythm sand oil layer could be resolved at extra high water cut stage by horizontal well can be solved, the potential of low permeability interval can be tapped and the producing reserves and the oil recovery can be improved. The development condition of intraformational bed is the key of many factors influencing the development effectiveness of horizontal well because the distribution of remaining oil is significantly influenced by intraformational bed during extra-high water cut period. Based on the development condition of intraformational bed in the thick positive rhythm oil layer and its influence on the distribution of remaining oil , the technology polices of horizontal well in tapping the potential had been worked out. Therefore the advantage of horizontal well can be brought into play.
- Asia > China > Shandong > North China Basin > Shengli Field (0.99)
- Asia > China > East China Sea > Bohai Basin > Jiyang Basin > Gudao Field > Guantao Formation (0.99)
- Asia > China > East China Sea > Bohai Basin > Jiyang Basin > Guantao Formation (0.99)
- Well Drilling > Drilling Operations > Directional drilling (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Conformance improvement (1.00)
Abstract Separate layer oil production technologies in Daqing Oilfield were developed and improved continually with the course of the oilfield development. The technologies in the medium-low water-cut flowing period were mainly composed of the oil well packers, the Model 625 oil well regulators and the multipurpose eccentric regulating & plugging control system. In the early high water-cut artificial lifting period, 4 types of mechanical water shutoff technologies including integrated, equilibrium, slip and drillable ones were developed and applied. Furthermore, the double fluid chemical water shutoff technology was successfully studied. In the late high water-cut artificial lifting period, the water detection technology by temperature log and the profile testing technology provide accurate guides in determining the high water-cut layers. Adjustable intervals mechanical water shutoff technology and the single fluid chemical water shutoff technology could meet the requirements of subdividing oil production and water shutoff for artificial lifting wells. 1. Introduction Daqing Oilfield is a heterogeneous multi-layer sandstone reservoir, whose exploitation strategy is to inject water to keep the reservoirs' pressure. The major oil reservoirs' physical properties are quite different from the secondary ones. During the water injection process, the water & oil distribution and the rule of their motion are extremely complex, commingled production method could lead the injected water underground easily to be finger advanced. Therefore separate layer oil production technologies that are suitable to Daqing Oilfield's real situation were developed in order to reduce these differences among layers, control rising water-cut, fully exploit each single oil layer, and provide vital technical support for high-efficiency oilfield development. Separate layer oil production technologies in Daqing Oilfield were developed and improved continually with the course of the oilfield development, which were fallen into three successive ones: the medium and low water-cut flowing period; the early high water-cut artificial lifting period and the late high water-cut artificial lifting period. This paper briefly introduces the development of separate layer oil production technologies in terms of each period's characteristics, and also presents the future developing direction of Daqing Oilfield. 2. The medium-low water-cut flowing period This period began from the early days of the oilfield exploitation to the end of the 1970s. At that time, the major exploiting reservoirs in Daqing Oilfield were high permeable layers in the main pays and the medium-high permeable layers in the nonpay zones. The separate layer oil production mainly aimed at controlling the injection into the high permeable layers, increasing the injection into the medium-low permeable layers and regulating the distribution of oil and water among layers and planes by the way of separate layer water injection. Therefore, the production from the medium permeable layers could compensate the production from the high permeable ones. When most layers produced water in oil wells and the high permeable oil reservoirs entered into the high water-cut period, it was necessary to enhance the development for medium-low permeable layers in order to reduce the differences among layers. Meanwhile, separate layer oil production and water shutoff measures were taken for high water-cut intervals. The separate layer oil production technologies in the 1960's, which were mainly composed of the oil well packers and the Model 625 oil well regulators, can divide the reservoirs into 4–5 intervals. Adjusting the size of unfixed nozzles in the Model 625 regulators can control each layer's production. As a result, the wells can produce oil from separate intervals quantitatively. The separate layer oil production technology with the Model 625 oil well regulators can effectively ease the contradiction among layers; exploit each oil layer with proportion rate; control the increasing water-cut rate; enhance the production and increase the recovery ratio. It has been applied at more than 2000 wells on site.
- Water & Waste Management > Water Management > Lifecycle > Disposal/Injection (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Yian Formation (0.99)
- Asia > China > Heilongjiang > Songliao Basin > Daqing Field > Mingshui Formation (0.99)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Conformance improvement (1.00)
- Production and Well Operations (1.00)
Abstract The China National Offshore Oil Corporation (CNOOC), Shell, and ConocoPhillips China, Inc., (COPC) are partners in the development of the XJG oil fields in the South China Sea. The XJG fields are in a mature production phase and challenge COPC (the field operator) with surface fluid handling capacity issues as a result of high water cuts. Additionally, there are no more slots available in the existing platforms for infill drilling. Typical completions include sand-control devices such as gravel packs and fracture packs inside 9 5/8-in casing with zones separated by packers and produced commingled through sliding sleeve doors (SSDs). In the past few years, more and more horizontal wells have been drilled and completed with expandable sand screens and premium screens. Most of the wells produce 10,000 to 15,000 BFPD using electrical submersible pumps (ESPs). In these commingled completions, the water cut rises from a few percent to 80% to 90% within the first 2 years of production. Typically, sidetracks are drilled before water cut reaches 96%, using the existing producing well slots. Production logs (PL) are routinely run to evaluate zonal fluid production for reservoir management and to screen for suitable candidates to perform water control operations during ESP changeout, workover operations. Quantitative PL evaluation in these deviated, high-flow rates, high-water-cut environments is challenging because of the uncertainty and inaccuracy of fluid holdup data acquired with conventional technology. Recently, PL data acquired with local probe holdup sensors have successfully diagnosed well production and provided guidance for workover operations to reduce water cuts and provide substantial incremental oil production. Additionally, caliper data associated with the local probe sensors is used to gauge completion diameter and to help verify perforation depth. Performing production logging in this challenging environment requires detailed prejob planning and careful job execution. Several cases of diagnostic evaluations and different water control operations performed are discussed in this paper. Introduction XJG oilfields are located offshore in the South China Sea around 130 km southeast of Hong Kong. These fields are sandstone reservoirs, consisting of three anticline structures bearing black oil. Discovered in 1984, the XJG fields are stacked reservoirs, producing from the XH formation of mid-Miocene age. The low GOR oil varies from 26º to 40º API saturating, usually unconsolidated sandstones with average porosity of 25% and permeability measured in the Darcy plus range. Aquifer support is strong, helping to sweep hydrocarbons but also causing rapid water breakthrough in high permeability layers. The shallower formations are prone to sand production, so the typical completions are internal gravel packs inside a 95/8-in casing producing through SSDs, into 27/8 in or 3 1/2-in tubing. The deeper, more consolidated formations do not require sand control and are completed with perforations inside 7-in or 9 5/8-in casing. More recently, short, lateral, horizontal sidetrack wells are being completed with expandable sand screens in openhole wells, making water control difficult to achieve. ESPs are used in all wells of the field to improve productivity. Typical well production rates are on the order of 10,000 to 15,000 BPFD. Field average water cut at this stage is around 84%. Present Challenges The XJG reservoirs are being developed using two fixed platforms. At this time, no additional slots are available for new well locations on either platform. This situation limits infill drilling to accelerate oil recovery. Oil recovery acceleration is accomplished either by sidetracking high-water-cut wells or performing water control operations on existing completions.
- Asia > China (1.00)
- North America > United States > Texas (0.46)
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > Asia Government > China Government (0.54)
- Well Completion > Sand Control (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Conformance improvement (1.00)
- Production and Well Operations (1.00)