Development Of Horizontal Wells Research Articles

Применение новых технологий кислотной обработки пластов для восстановления продуктивности пласта

Oil recovery, measured by the oil recovery factor (ORF), is a key indicator of the efficiency of oil production. In Russia, the ORF decreased to 0.3 while in the United States this indicator increased to 0.4. About 90% of Russian oil is produced by large holdings, the structure of reserves is shifting towards hard-to-recover, which requires the use of new methods to increase oil recovery. Primary and secondary production allows only 20-50% of oil to be extracted, what makes the use of tertiary methods necessary. The development of horizontal wells with multistage hydraulic fracturing contributes to the development of new field sites, but requires careful preparation of wells to minimize risks and cost increases. Cleaning the bottomhole area using acidic formulations is often the only cost-effective way to restore the productivity of a horizontal well. The improved method of acid composition reduction using a guar gel with delayed “crosslinking”, which ensures uniform treatment of all productive zones of the formation is considered in article. The technology allows for continuous multi-stage acid treatment, temporarily blocking highly permeable areas and increasing the coverage of acidic effects on poorly drained areas. The calculation of the diverter volume considers the average efficiency of the liquid after mini-fracturing, adjusting the volume depending on the efficiency of the liquid at each port.

Research and Practice on Implementing Segmented Production Technology of Horizontal Well during Extra-High Water Cut Stage with Bottom Water Reservoir

Bohai X oilfield has reached the extra-high water cut stage of more than 95%, dominated by the bottom water reservoir. The oilfield mainly adopts horizontal-well exploitation, with the characteristics of high difficulty and low success rate for well water plugging. To solve the above problem, the segmented production technology of horizontal wells was developed to guide oilfield applications and tap their potential. In the segmented design stage, the horizontal section is objectively segmented by drilling condition analysis, optimally based on drilling through interlayers or permeability discrepancy formation, simultaneously combined with the numerical simulation method. When implementing measures, annulus chemical packer materials are squeezed between segments to effectively inhibit the fluid flow between the open hole and the sand-packing screen pipe. Moreover, the packers are used to seal between segments to effectively restrain the flow between the screen and the central tube, achieving the establishment of compartments. In the production process, the valve switch on the central tube can be independently controlled by a remotely adjustable method to achieve optimal production. This segmented production technology was successfully tested for the first time in Bohai oilfield. Up to now, a total of six compartment measures have been implemented, remarkably decreasing water cut and increasing oil production for horizontal wells in the bottom water reservoir. This method does not require water testing, and the optimal production section can be chosen through segmented independent production, greatly improving the success rate of water-plugging measures for horizontal wells. This technology opens up a new mode for the efficient development of horizontal wells in bottom water reservoirs and is planned to be widely promoted and applied in similar oilfields.

Mathematical Modeling of Prediction of Horizontal Wells with Gravel Pack Combined with ICD in Bottom-Water Reservoirs

During the development of horizontal wells in bottom-water reservoirs, the strong heterogeneity of reservoir permeability leads to premature bottom-water breakthroughs at locations with high permeability in the horizontal wellbore, and the water content rises rapidly, which seriously affects production. To cope with this problem, a new technology has emerged in recent years that utilizes gravel filling to block the flow in the annulus between the horizontal well and the borehole and utilizes the Inflow Control Device (ICD) completion tool to carry out segmental water control in horizontal wells. Unlike conventional horizontal well ICD completions that use packers for segmentation, gravel packs combined with ICD completions break the original segmentation routine and increase the complexity of the production dynamic simulation. In this paper, the flow in different spatial dimensions, such as reservoirs, gravel-packed layers, ICD completion sections, and horizontal wellbores, is modeled separately. Furthermore, the annular pressures at different locations are used as the solution variable for the coupled solution, which realizes the prediction of oil production, water production, and the water content of gravel packs combined with ICD completion of horizontal wells. The model is used to calculate the effects of different crude oil viscosities, different reservoir permeabilities, different permeabilities of gravel-packed layers, and different development stages on the water control effects of gravel packs combined with ICD completions and conventional ICD completions under field conditions.

Research on Microscopic Pore Structure Characteristics and Producibility of the Chang 9 Reservoir in the Wucangpu Block

The pore structure can affect the storage and flow properties of rock, which is an important research content in the study of unconventional tight reservoirs. This research hopes to clarify the reservoir characteristics and fluid seepage mechanism of the Chang 9 reservoir in the Wucangpu block and provide technical support for the development of horizontal wells with staged fracturing in this block. In this paper, the microscopic pore structure characteristics and producibility of the reservoir in the study area are analyzed in detail by means of constant-rate mercury intrusion and nuclear magnetic resonance. The research results show that the reservoir with permeability less than 0.076 mD is mainly composed of microthroat, the reservoir with permeability of 0.208-0.633 mD has a larger proportion of microthin throat, and the reservoir with permeability of 2.722-3.998 mD has a larger proportion of fine-middle throats. The results show that the oil/gas in the rock sample reservoirs with permeability greater than 1.0 mD is easy to produce.

Study on sustained-release kinetics of intelligent tracer for water search in horizontal wells

At present, finding and plugging water in horizontal wells has become both the main difficulty and also the key for the sustainable and effective development of horizontal wells. Intelligent tracer technology for finding water can directly indicate the position and intensity of water outlets in a horizontal interval and it has broad application prospects. Currently, however, the interpretation of this technology in the field assumes that the intelligent tracer in each section of the horizontal well is released at an equal speed, which reduces the reliability of interpretation results. In order to improve the interpretation model for finding water in horizontal wells with intelligent tracers, it is necessary to further clarify the controlling factors of intelligent tracer release and its variation law. Therefore, using an independently developed water-soluble intelligent tracer, macroscopic static and dynamic release experiments were carried out, as well as CT scanning microscopic experiments, and a one-dimensional sustained-release dynamical model of the intelligent tracer was established based on the microexperimental results. A static non-scour experiment showed that the polymer skeleton is the fundamental reason for the tracer's sustained release. A dynamic scour experiment showed that temperature and external scour flow rate are the main factors affecting the release of intelligent tracer and that the greater the temperature and scour flow rate, the greater the cumulative release amount. Microcosmic release experiments showed that the release of intelligent tracer is a process of gradual dissolution from outside to inside, as well as diffusion from outside, with an obvious dynamic interface. Furthermore, the results of the dynamic model analysis were in agreement with those of the macroscopic scour experiments. The results of this study confirm that the influence of temperature and scour speed on intelligent tracer release should be considered in the interpretation model of intelligent tracer water search in horizontal wells, and they provide guidance and have practical significance for expanding the application of these tracers in oil and gas field development.

The problem of high water cut in the products of horizontal wells

Background. The production of oil and gas by horizontal wells, despite all its advantages, is subject to exploratory and operational complications. At the final stage of their development, such fields become hard-to-recover reserves. Production of oil and gas is often associated with a high water cut, a significant drop in reservoir pressure, and precipitation of asphaltene deposits.Aim. To analyze the problem of early indication of flooding of horizontal wells and do research on existing solutions nowadays.Materials and methods. The dependence of the logarithm of the water-oil ratio on the cumulative oil production was investigated. An analysis of production decline curves was carried out, along with a graphical diagnostics of flooding evolution.Results. The anticipated cumulative production of a well was determined by continuing the linear dependence to its economic limit. A graph was plotted in semi-logarithmic coordinates for the analysis of production decline curves. According to the dependence of the water-oil ratio versus time, the type of early well flooding was determined in logarithmic coordinates.Conclusion. One of the most significant problems in the development of horizontal wells consists in the high water cut of the obtained products. According to the data for 2020, the average water cut in the main fields of Russia comprises at least 85%, with the mass ratio of produced oil and associated water approaching 1:7. The use of water-soluble polymers for waterproofing of horizontal wells can be considered a promising direction due to their efficiency in limiting water inflow in vertical and directional wells.

Differences in production decline characteristics of horizontal wells in tight gas sandstone reservoirs with different qualities: A case study of the Sulige gas field, Ordos Basin

Development of horizontal wells is one of the important means to improve the well production of the tight gas reservoir and realize the effective development of tight gas. Based on abundant static and dynamic data of a large number of horizontal wells that have been put into operation, structure characteristics of a tight reservoir carried out, detailed geologic analysis of the effective reservoir drilled by horizontal wells, and development dynamic analysis, three effective reservoir lateral distribution modes of the block concentrated development mode, medium layer, and thin layer superimposed mode and thin layer isolated model mode are proposed and their adaptability to the horizontal well deployment is evaluated. The drilled reservoir is divided into three types: high-quality reservoir, suboptimal reservoir, and poor reservoir, and the quantitative classification standard is established. On this basis, the decline rule and the difference of horizontal well drilling in different quality reservoirs are discussed, and the quantitative evaluation standard of the horizontal well development effect is established. The initial decline rates of the three types of horizontal wells are 32.9%, 35%, and 40%, and the estimate ultimate recoveries (EURs) of three types of horizontal wells are 89 million cm3, 68 million cm3, and 31 million cm3, respectively. The results of this study provide technical support for the optimal deployment of new horizontal wells in the Sulige gas field and a reference for the development of horizontal wells in the same types of gas reservoirs.

DETERMINATION OF THE OPTIMAL DESIGN OF THE HORIZONTAL BOREHOLE

The article presents the development of approximate and accurate methods for substantiating the optimal design of horizontal wells for their productivity. Universal recommendations have been developed that are suitable for use in the development of horizontal wells of deposits of any complexity. The main operational facilities of the oil fields of the Republic of Kazakhstan are at a late stage of development. The reserves of these objects are difficult to recover, which is due to factors such as high oil viscosity, low permeability of reservoirs, as well as high layer-by-layer and zonal heterogeneity, low effective thickness of reservoir layers, the presence of sub-gas zones and lowpower oil fringes. Residual hard-to-recover reserves require the introduction of new technologies. The technology of drilling horizontal wells has huge prospects associated with the possibility of increasing the efficiency of oil production, extending the period of waterless operation of the well and increasing the oil recovery coefficient, involving in the development of reservoirs with low reservoir properties and high-viscosity oil, reducing depression on the formation and the effect of cone formation. The growing interest, worldwide, in the use of horizontal wells, there is a need to develop a theory and study the processes of fluid filtration to the bottom of these wells, taking into account the above factors, and this becomes an urgent scientific and practical task.

Drilling Technology for Long-Offset 3D Horizontal Shale Oil Wells in the Longdong Area of the Changqing Oilfield

Ravines and gullies criss-cross the shale oil reservoirs of the Longdong Area in the Changqing Oilfield, where there are also numerous protected zones for water and forest resources, plus prime farmlands. The development of horizontal wells is greatly restrained by the topography and protection zones, and the offset of 3D horizontal wells directly affects the number of horizontal well platforms and the factory-like operation of large platforms, and affects the effective utilization of subsurface resources. Based on the analysis of the characteristics and drilling difficulties of long-offset 3D horizontal wells, the wellbore profile design was optimized, and kick-off points, azimuths, deviation angles, and well sections for eliminating offset were selected to improve the control mode of hole trajectories. In the absence of a rotary steering system, conventional positive displacement motors (PDM) and polycrystalline diamond compact (PDC) bits were upgraded. In addition, tools for reducing friction and a water-based CQSP-4 drilling fluid system suitable for long-offset horizontal shale oil wells were employed. Finally, the drilling technology for long-offset 3D horizontal shale oil wells in the Longdong Area was developed. This technology was applied to 6 3D horizontal wells with offsets over 900 m in Longdong Area. Friction torque was reduced significantly and the drilling process was safe and efficient, with good field application effect achieved. The successful application of the technology can support factory-like efficient development of the large shale oil platforms in the Longdong Area, which have multilayered systems and multiple drilling rigs. Further, it can facilitate the transformation of the drilling operation mode from single-rig and single-team to industrialized and clustered production.

Experimental study on EOR performance of CO2-based flooding methods on tight oil

The recovery of tight formation is fairly low after depletion, and the poor physical properties make it difficult for water to be injected. And when the oil is with high wax content, it is more difficult to develop. Recently, with the development of horizontal wells and multi-stage hydraulic fracturing, the problem of injectivity is solved to some extent. With these techniques improving injectivity of displacing fluids, this paper conducted a series of coreflood experiments, including CO2 flooding, water alternating gas (WAG), carbonated water injection (CWI), active carbonated water injection (ACWI) and active carbonated water alternating gas (ACWAG), to investigate the EOR performance of CO2-based methods on tight oil. Furthermore, the influences of injected volume, surfactant concentration and water-gas-ratio on recovery were investigated. It is the first time to explore the feasibility of CWI/ACWI/ACWAG on increasing the recovery of tight oil with high wax content.Experimental results revealed that ACWAG achieved the highest oil recovery (63.04%) among all methods. In addition, CWI yielded an oil recovery of 60.67% and it is the highest among WAG, CO2 flooding and CWI with the same amount of CO2 injected. ACWI reached 54.17% original oil in place (OOIP) with 0.5 pore volumes (PV) of active carbonated water injected. In this study, water-gas-ratio has not demonstrable influence on EOR performance. This paper uncovers the potential and application of CWI/ACWI/ACWAG in enhancing recovery of tight oil with high wax content.

Research on Improving Accuracy of MWD Based on Support Vector Classifier and K-Proximity Method

With the development of horizontal Wells and extended reach Wells in the field of oil and gas exploitation, it is of great significance to the development of MWD which can measure the drilling trajectory in real time. Therefore, in recent years, Measurement while drilling (MWD) has been widely recognized and rapidly developed in the field of precise target drilling. Accelerometers and fluxgates are related to well trajectory measurement in the MWD. The external environment and the processing and installation error of the sensor lead to some errors in the measured value. Deviation caused by environmental interference and installation error leads to the low control precision of drilling tool attitude. In view of the shortcomings of the current calibration methods and the time-consuming and complicated operation of the traditional tri-axis orthogonal inclinometer calibration, this paper proposes the attitude error calibration method of the MWD based on the support vector classifier and the K-proximity method. First, a neural network model is established based on the measured calibration results and the measurements errors. Then, the K-proximity method is used to further classify the drill tool attitude data, and a neural network model combining the K-proximity method is constructed. Secondly, the software and hardware experimental platform for on-line calibration of the slant meter while drilling is built by using the calibration frame and the geomagnetic sensor. Finally, the experimental results showed that the mean deviation of well inclination angle and tool face angle is controlled within ±0.2°, and the mean deviation of azimuth is controlled within ±0.5°, which verified that the algorithm can increase accurate of drilling tool attitude.

Investigation of Productivity Prediction Method for Horizontal Wells in Gas Reservoirs with Closed Bottom and Top Boundaries

This study aims to predict the productivity of an open-hole horizontal gas well (OHHGW) in a gas reservoir with closed bottom and top boundaries (GRCBTBs). First, according to the theory of mirror imaging, an OHHGW in GRCBTBs is transformed into an infinite well array in infinite formation. Second, based on conformal transformation principle, the infinite well array is transformed into two production and two injection wells in the complex plane. Finally, according to the superposition principle of potential, a new productivity prediction method, which is suitable for the horizontal well in GRCBTBs, was developed. The field measured data of Jingbian gas field of Ordos Basin demonstrate the ability of the method to accurately predict the productivity of the OHHGW in GRCBTBs, and the prediction relative error of absolute open flow of well Longping 1 is only 1.03%, that is to say that the method proposed in this study has a certain guiding significance for the development of horizontal wells in GRCBTBs.

Study of massive water huff-n-puff technique in tight oil field and its field application

Based on the characteristics of horizontal oil wells in tight reservoirs during their late stage, which are exploited by elastic drive of natural energy and stimulated by large-scale volume fracturing; the massive water huff-n-puff technique is proposed for the use of supplementing the energy of the depleted formations, which can effectively increase the productivity of single horizontal oil well in addition to its financial benefits. In this paper, the massive water huff-n-puff technique is defined and discussed from the following aspects of the mechanism, reservoir engineering, laboratory experiments and so forth. Additionally, comprehensive analyses of the advantages of applying this technique in the development of tight oil reservoirs are provided. By the studies of the pressure composition diagram and the definition of residual injection pressure (RIP) in reservoirs, a massive water huff-n-puff mathematical model was established and the critical parameters for water-flooding were calculated. Laboratory experiments of this technique have shown that it can induce a certain number of micro-fracture networks and its application in actual oilfields also shown positive results. The pilot tests have achieved remarkable increases in productivity and economic benefits. For example, the average daily oil production from a single well is increased by 4.5 t/d (0.8 → 5.3 t/d), the formation pressure has increased by 9.3 MPa (6.9 → 16.2 MPa), accumulated oil production has reached 1,987t, and its input-output ratio has shown an enhancement in the range of 1.00:1.74–1.00:4.06. The research results of this technique provide a new way and an important model for efficient development of horizontal wells in tight oil reservoirs.

NMR study on pore structure and permeability of different layers of deep low-rank coal

ABSTRACT The difference in the development of coal pore system in bedding direction is of great significance to the exploration and development of coalbed methane and the prevention and control of gas disasters. In order to improve the understanding of the fluid storage and transportation rules in the development of horizontal wells for coalbed methane, the typical low-rank coals in western China are taken as the research object. Based on the NMR experiments, the effective pores, pore size distribution and pore connectivity of low-rank coals in parallel and vertical bedding directions are analyzed. Meanwhile, the reason for the difference in pore structure of parallel and vertical bedding coal is also explained. The results obtained are as follows: (1) All types of pores in low-rank coal are developed. The proportion of T 2 spectrum area of large pores in parallel and vertical bedding coal samples is 55% and 43%, respectively. After centrifugation, the T 2 spectral area of large pore peaks in parallel bedding coal samples reduced more than 85%, and the vertical bedding was reduced by 80%, indicating that the large pores in the coal sample were developed and the pores communicated with each other and had good connectivity, and most of the water escaped from the medium and large pores. (2) The total porosity, effective porosity, and movable fluid saturation of the parallel bedding are all larger than the vertical bedding, and the parallel bedding T 2 C is less than the vertical bedding at about 1 ms, indicating that the permeability of the parallel bedding is better than the vertical bedding. (3) The hole was squeezed more seriously in the vertical bedding direction, and the micro-cracks extended along the bedding direction. However, the poor continuity in the vertical bedding direction is the main reason for the difference in coal structure between the parallel bedding and vertical bedding directions.

Application of binary compound water control technology in the development of horizontal wells in offshore oil fields

Offshore A oil field is a typical bottom water reservoir with thin thickness of oil layer and large thickness ratio of water layer and oil layer. Due to its strong bottom water energy, serious non-homogenous and the impact of the bottom ridge, most of the horizontal well production segment is seriously water out.Based on interaction relationship between horizontal segment trajectory and oil and-water interface, the distribution and contrast of permeability along horizontal segment and the comprehensive analysis of production performance, this paper combines the characteristics of the residual oil distribution of typical wells and the mechanism of dual compound oil addition, and from the perspective of combining theory with the field creatively put forward the dual composite water control mode of first injecting gel segment plug and then injecting foam. then completed the design of dual compound water control mode and dosage of the typical well. After processing water control measures, the production data shows that the water content decreased significantly after opening the well, from 95.1% before water control to 80%, which was 15% lower. Also the oil production rate has a significant increase from 2.3t/d before water control to maximum to 9t/d after implementing control measures and cumulative oil increase is 550t with effective period of 135 days. The effect of oil and precipitation is obvious.

Application of micro-seismic monitoring technology in fracturing and water injection development of horizontal wells with low permeability and thin layer

With the development of unconventional oil and gas reservoirs, microseismic monitoring has been developed rapidly as the key technology of hydraulic fracturing design, implementation and evaluation of this type of oil and gas reservoir. A oil field test area as a low-porosity and low permeability reservoir, the micro-seismic monitoring data were collected and processed during the development of fracturing horizontal well fracturing. The spatial development characteristics of the length, width and azimuth of the artificial fracture zone are analyzed by the method of overlooking the projection, fracturing and front edge calculation of the microseismic event point, and the later stage water injection is instructed to provide technical support for the future design of the horizontal well encryption and adjustment scheme.

EVALUATION OF THE INFLUENCE OF THE UNDERLYING WATERS FOR DEVELOPING OF HEAVY OIL RESERVOIR PK1-3 OF THE VOSTOCHNO-MESSOYAKHSKOYE OIL FIELD BY USING WELL TESTS

The article presents the experience in the stage of experimental industrial exploitation and industrial exploitation of the field with a system for the development of horizontal wells with non-standard oil properties (high oil viscosity) and complex geological structure (gas cap and aquifer). The focus of the article is on the estimation of aquifer activity by using well tests.

Study on Drilling and Completion Techniques of Horizontal well for Coalbed Methane

Due to the unique reservoir characteristics of the coalbed methane (CBM) in China, many technical problems have to be studied and solved in the development of horizontal wells for CBM. In this paper, based on the V-type wells, we have summarized the many techniques involved in Drilling and completion of horizontal well for CBM in Binchang mining area, such as leakage protection and sealing, geosteering while drilling, remote connection, variable density cementing, Coal seam cavitation, fiberglass casing running into the well, and etc. It is pointed out that the air foam under-balance drilling will be the development direction for coalbed methane drilling technology.

Application of Research of the Relationship between Ground Stress and Fractures in the Trajectory Optimization of Horizontal Wells

From the perspective of improving single well production and wellbore stability, stress field and natural fractures are the factors which have to be taken into account in the development of horizontal wells of the complex carbonate oil and gas fields in Kuqa piedmont and platform-basin transitional area. On the one hand, as the present stress field is the key factor to control fracture permeability, the trajectory of horizontal wells should pass through fracture system with good permeability as much as possible, being conducive to the effective stimulation of the reservoir. On the other hand, at the state of specific stress, the stability of well trajectory varies with directions. Therefore, before drilling horizontal wells, it is necessary to fully analyze the quantitative relationship between the present stress state and natural fracture occurrence and mechanical characteristics, etc., to optimize and determine a well trajectory conducive to high yield and wellbore stability. In this study, firstly, the fundamental principles for evaluating the present stress state and analyzing the relationship between the stress and fractures were described. Then based on the relationship between them, the occurrence and longitudinal positions of permeability fractures were analyzed. Apart from that, the stability index and fracture opening pressure distribution of wells in different directions at given stress state and fracture system were also analyzed. Finally, the optimization scheme for trajectory of horizontal wells under complex conditions was discussed with three aspects taken into account, i.e. best drilling in permeability fractures, wellbore stability and drilled reservoir stimulation.

Horizontal drilling assessment in Western Canada

The first horizontal well was drilled in Saskatchewan in 1987. Since then, the number of horizontal wells drilled has escalated rapidly, averaging approximately 500 per year since 1993. When combined with horizontal wells drilled in Alberta, the major Canadian oil-producing province, the total number drilled in 1995 was 978. This total exceeds the National Energy Board (NEB) projected maximum of 816 wells per year. The NEB projections were based on a break-even point for the drilling of horizontal wells of a return of CDN $285,000 using a discount rate of 15%. This corresponded to a cumulative production from each individual well of some 11,000 m3. The introduction of a royalty-free production volume of 12,000 m3 per horizontal well in Saskatchewan was instrumental in stimulating the rapid expansion in the use of horizontal wells and helping Canada to exceed the forecasted drilling level. Within Saskatchewan, daily production from 1964 active horizontal wells is in excess of 20,000 m3. Comparative analysis indicates that the average daily production per well has increased from approximately by 40% with the advent of horizontal wells. In total production terms, provincial production has increased from 11.7 million cubic metres in 1989 to 20.9 million m3 in 1996. This represents an increase of almost 79% based primarily on the extensive use of horizontal wells. In 1996, horizontal wells produced 36% of the province's oil from 12% of the active wells. In the southeastern producing area of Saskatchewan, the Williston Basin, declining oil-production has jumped 100%, with horizontal wells accounting for approximately 50% of total regional production. Pay zones in this area, as in most of the province, tend to be relatively thin, with net pay frequently less than 5 m. The modest investment of some CDN $5 million in government research funding 10 years ago to simulate the development of horizontal wells, combined with a favourable royalty structure, has been at least partially responsible for very significant benefits to the provincial economy. In Saskatchewan, horizontal wells have (i) paid over CDN $400 million in royalties since 1990, (ii) annually generated CDN $525 million in investment and (iii) sustained 4350 jobs. Details pertaining to the Winter Cummings Sand Pool and others as examples of the success of the horizontal well program in Saskatchewan are discussed in this paper.