The southern margin of the Junggar Basin is a strategic successor for oil and gas exploration, and the strategic breakthrough in exploration well Gao 1 further proved the promising future of the lower assemblage in the southern margin. According to the results of sectional structural modeling, structural analysis of the trap and the matching between accumulation conditions, the controlling factors of hydrocarbon accumulation in the lower assemblage was identified. The study results indicate (1) the lower Jurassic is primary source rock which has a large potential; the Cretaceous Qingshuihe Formation, Jurassic Toutunhe Formation and Khalza Formation are effective reservoirs with a certain scale; and the regional thick mudstone of the Cretaceous Tugulu Group at higher pressure is effective caprock with good sealing ability; (2) static elements (i.e. source, reservoir and cap rocks and traps) matched well in space, and dynamic elements matched well in time:the traps developed earlier, the forming of the structure was well consistent with the generating of hydrocarbon, later reconstruction was weak and the preservation conditions were good, which are good conditions for large-scale accumulation. Base on the comprehensive analysis above,near-source anticlinal traps, such as the Tugulu anticline, the Hutubi anticline and the Dongwan anticline, are proposed to make breakthrough to gas exploration in the southern margin of the Junggar Basin.

Geology-engineering integration is widely recognized as an effective process in the exploration and development of unconventional oil and gas reservoirs. It involves massive data of various disciplines including geology, reservoir, geophysical exploration, drilling, mud logging, well logging, well test, production test, production and downhole operations. Since professional personnel/organizations have different understandings and requirements for specific data, the data systems can hardly be connected and interacted among disciplines, which may form "data islands". Based on the system platforms of data lake and knowledge database for the life cycle of reservoirs, the core data of geology and engineering are selected and the core "gold data" of exploration and development are identified to realize convenient and efficient communication and interactive optimization of professional data. In this way, the geology-engineering data can be integrated to greatly improve the efficiency and accuracy of data utilization. For purpose of effective geology-engineering integration, an integrated project organization and management framework is proposed, and the decision-making, coordination and information feedback mechanisms are established. Moreover, more sophisticated technology management is implemented, and key links in production arrangement and implementation are optimized. Thus, the best economic benefits can be expected.

With the deepening geological knowledge and the advancing exploration techniques, the exploration in Pingbei slope belt, Xihu sag of the East China Sea Shelf Basin, is shifting from structural reservoirs to lithologic reservoirs. According to the systematic analysis of transitional deposits, Pingbei slope belt is believed having four sequence stratigraphic styles, i.e., fault-slope, opposite fault terrace, antithetic fault terrace, and concordant fault terrace, which correspond to four types of sandstone reservoirs (fault-slope tide-dominated delta tidal channel, opposite fault terrace tide-dominated delta front tidal flat, antithetic fault terrace river-dominated delta front channel, and concordant fault terrace river-dominated delta front channel). Based on the sand body distribution and hydrocarbon accumulation models predicted, the formation conditions and distribution rules of lithologic reservoirs in different plays of Pingbei slope belt were identified. It is finally indicated that the sandstone reservoir of fault-slope tide-dominated delta tidal channel in Tuanjieting area and the sandstone of concordant fault terrace river-dominated delta front channel in Qongqueting area are primary exploration targets. Following the model of lithologic reservoirs, significant breakthrough has been made during drilling lithologic traps in Block Ningbo 19 controlled by Baoyunting low uplift and the antithetic fault terrace belt.

The gas-rich Kelasu structural belt is the primary option for increasing reserves and production in the Tarim Basin. The geological and engineering conditions in the belt are extremely complex as a result of strong orogenic movements, represented by deep burial (VD 7000-8000 m), high temperature (130-190℃), high pressure (116-136 MPa), high in-situ stress (130-180 MPa), low porosity (4%-8%), low permeability (0.01-0.1 mD), thick gravel (5500 m), thick salt-gypsum (4500 m), and large dip angle (87°). These factors bring great challenges to the safe and economical exploration and development. In order to get fast drilling and production, guided by the geology-engineering integration, the multi-disciplinary research team worked in an innovative and integrated manner to figure out the solutions to ultra-deep complex gas reservoir development with higher rate, productivity and quality. By combining precise prediction of key zones, customized design of drill bit and oil-based drilling fluid system, the all sections were drilled in a safe and rapid mode. According to sweet spots prediction, fracture evaluation and classification, an optimal fracturing stimulation process was established based on fracturability of natural fractures. Considering formation and fluid properties and working conditions, a system barrier was designed for ensuring wellbore integrity. By virtue of improving geology-engineering integration practices, the drilling period of an ultra-deep well reduced from 336 days during the 12th Five-Year Plan period to 277 days in 2017, the average single-well productivity increased by 4-5 times, and the well integrity was improved. Thus, the geology-engineering integration is a technical guarantee for safe and economical development of ultra-deep complex gas reservoirs in the Kelasu structural belt.

The Changning National Shale Gas Demonstration Zone is a representative case in China's shale gas industry. Its development has transited from the engineering exploration and practice initially to the comprehensive geoengineering integration in the third stage. For purpose of "single-well production increase and overall efficiency improvement", it is necessary to make full use of various geological and engineering data to systematically study four optimal key elements:horizontal well box, fracturing stimulation, production system and development technology, aiming to continuously increasing production from single well to full gas field, and improving the estimated ultimate recovery (EUR) and economic indicators. A 3D shared geoscience model based on geoengineering integration can perform system analysis and evaluation of project implementation effects by multidisciplinary and multi-parameter data analysis, multi-field coupled simulation on stress-sensitive shale (including geomechanics, modeling hydraulic fracture network and gas reservoir numerical simulation) and full gas field numerical simulation. By comparing multiple programs under current technical conditions, optimal box position and production system have been defined. Also, fracturing parameters and process, well location and spacing have been established. In order to achieve overall optimization, it is proposed that geoengineering integration should transform from well-based integration of drilling, completion fracturing and production to full gas field-based development project. As a response, numerical simulation to stress-sensitive shale was carried out on full gas field for the first time at home and abroad.

Several analytical methods, including casting thin sections, constant-rate mercury intrusion, high-pressure mercury intrusion, low-temperature liquid nitrogen adsorption, stress sensitivity, and water locking damage, were used to investigate the microscopic pore structures and causes for low production of tight sandstone gas reservoirs in the 8^th member of Shihezi Formation, Permian, Upper Paleozoic ("He 8^th member"), Ordos Basin. Then, a solution based on geology-engineering integration was proposed for increasing single-well production. The study shows that the He 8^th member tight sandstone reservoir comprises secondary dissolved pores such as lithic dissolved pores and intercrystal pores, without fractures, indicative of a single-porosity reservoir. The peak throat radius is 0.2-2.2 μm. The pore volume communicated by nearly nano-throats in the reservoir with permeability less than 1 mD is greater than 38%, suggesting as micro-throat reservoir where the micro-throats control the permeability. Under the action of stress, micro-throats are prone to shrinking, closing and quickly absorbing when exposing to water, so that they are stress-sensitive and likely induce water locking damage. In addition, the single sand body is small in scale and low in abundance, so the single-well production is generally low. The solution based on geology-engineering integration for increasing single-well production mainly involves four aspects. First, geologic sweet spots with rich gas and engineering sweet spots in fracturable reservoirs are preferred for development with lower cost and higher efficiency. Second, a specific and customized stimulation program is designed depending on the reservoir characteristics. Third, volume fracturing is applied to increase the stimulated reservoir volume (SRV) through changing the single-porosity reservoir to a dual-porosity (pore-fracture) reservoir and weakening the control of micro-throats on the permeability. Horizontal wells are preferentially deployed along primary channels with ideal vertical connectivity to expand the drainage area. Fourth, multi-layer/zone commingled production is adopted to enhance the single-well productivity.

The Tuha oilfield has various types of reservoirs. To produce more reserves from complex reservoirs, precise management based on geology-engineering integration has been implemented with the support of advanced technologies, contributing to the low-cost exploration of complex reservoirs. A series of supporting techniques have been developed and improved. First, the ROP enhancement technique together with optimized casing program, and completion/logging design, help greatly reduce the drilling period and cost. Second, the technique based on geology-engineering integration is proposed to further investigate hydrocarbon accumulation mechanism and accurately predict reservoir sweet spots, so as to facilitate the optimization of exploration scheme. Third, the geosteering technique is developed to improve drill-in rate of horizontal wells. Fourth, special drilling fluid system and shallow horizontal well drilling techniques ensure safe and fast drilling operation with good quality. Fifth, the horizontal well + volume fracturing technology is promoted and improved for maximizing the recovery of reserves. These techniques have contributed several breakthroughs in the Tuha oilfield, with bulk reserves discovered.

After developing for more than 20 years, the main part of the Zanazour oilfield in the pre-Caspian Basin, has demonstrated high recovery efficiency and low reservoir pressure. However, the marginal reservoirs with low permeability and thin pay remain a challenge for effective development, with only low productivity by conventional vertical wells. To develop these low-permeability and thin reservoirs, a horizontal well geology-engineering integration technology system was proposed, and a series of research and field test were carried out. This technology system organically integrates drilling and completion, staged fracturing and oil production engineer with consideration to geologic and reservoir characteristics. It is manifested in six aspects. First, the lowest effective porosity is reduced from 8% to 4%-5% considering the influence of horizontal well staged fracturing on production. Second, preferable target layers are selected and horizontal section orientation is determined depending on stress distribution, orientation of induced fractures, and thickness and distribution of pay zones comprehensively. Third, rotary geosteering and LWD techniques are combined to increase the drill-in rate of thin layers (1.4-6.1 m) from 20.7% to 72%. Fourth, multiple measures are taken to improve the cementing quality in horizontal section and the resistance to impact by perforation and fracturing operations. Fifth, the staged fracturing design and parameters are optimized in accordance with the principle of "one design for on stage" by considering the heterogeneity of horizontal section. Sixth, gas lift and liquid nitrogen assisting flowback techniques are adopted for low-pressure reservoirs. The technology system has been successfully applied in development wells (e.g. H8) in marginal reservoirs. Well H8's post-fracturing production is 11 times of the adjacent well. So far, field test has been completed in 8 wells, revealing a cumulative oil production added by 11×10⁴t. Thus, the geology-engineering integration technology system represented by staged fracture is proved efficient for low-permeability and thin marginal reservoirs.

In southern Songliao Basin, tight oil was generated in upper formations and preserved in lower formations in the Fuyu Formation. With insufficient hydrocarbon charging, large-scale continuous tight lithologic reservoirs were formed. They can hardly be economically developed because of the strong heterogeneity, low permeability (<0.5 mD), low oil saturation (<50%), high water content (>80%), and low mobile fluid content (<20%). To facilitate the development of tight oil, fine reservoir description was carried out, and then, favorable structural setting and high gas-to-oil ratio were clarified as key factors controlling oil accumulation and productivity. On this basis, the techniques were developed to identify "seismic sweet spots", "development sweet spots" and "fracturing sweet spots". Thus, the drilling and stimulation performance of tight oil horizontal wells has been improved. Coupled with new operating mechanism, integrated management and market-oriented operation, the Fuyu tight oil reservoir has been economically developed in the Qian'an area, southern Songliao Basin.

Tight oil reservoirs are widely distributed and have a huge resource potential in the Daqing oilfield. For effective development of such tight oil reservoirs, the fracturing stimulation based on geology-engineering integration was proposed. Specifically, the pad-based fracturing scheme was optimized to combine geologic, drilling and fracturing data with operation procedures, maximizing the stimulated reservoir volume. Following an intensive factory-like operation mode, the number of field staff was reduced to 26, and the covering area was saved by 77%. With one package of fracturing truck, the fracturing operation was completed in 154 stages of 9 horizontal wells in Block Fang 198-133 within 32 days. Accordingly, a set of specific factory-like fracturing specification for Daqing oilfield was established. As a result, 1.55×10⁴m³ of oil or 38.1m³ per well per day has been produced during 158 days after fracturing stimulation, which is 14 times higher than the vertical well stimulated in the block. With the increase of productivity and efficiency, the comprehensive operating cost was reduced by 36%. Thus, the tight oil reservoirs in the block were fully recovered and developed economically and effectively. And the practices are significant to the production improving of tight oil reservoirs in other blocks of Daqing oilfield.

Compared with the shale gas fields in North America and the Sichuan Basin, the Zhaotong National Shale Gas Demonstration Zone is characterized by micro-relief structures with developed fractures, poor stress conditions and narrow target reservoir window. In this zone, it is hard to control the trajectory of a horizontal well and develop efficiently. Considering geological and engineering factors, a model was proposed for increasing ROP and production efficiency by controlling trajectory at low cost. The model emphasizes geological optimization in pre-drilling, drilling and post-drilling analysis to understand the distribution law of high-quality shale reservoirs and technical designing. It ensures the precision in landing and tracking horizontal section by integrating techniques including element mud logging + gamma ray control while drilling, point-by-point seismic guidance, ant tracking + apparent polarity attributes, and geosteering tools. It ensures drill-in rate and smooth trajectory, improves drilling quality and lays a solid foundation for high gas production. The proposed geosteering technology has been successfully applied in field.

The Shengli oilfield is rich in tight oil reserves, but the reservoirs characterized by deep burial, poor physical properties and complex lithology, leading to unsatisfactory development performance like low yield and fast production decline after conventional fracturing stimulation. Through researches and optimizations, new fracturing techniques, such as commingled fracture network stimulation, were developed for tight oil reservoirs. While increasing the stimulated reservoir volume (SRV), these techniques can greatly improve fracture conductivity and post-fracturing performance. For the reservoirs with multiple layers vertically, two types of treatments were established, i.e. multi-stage fracturing of horizontal wells and multi-stage fracturing of vertical/deviated wells. A fast-dissolving low-concentration guar fracturing system that can be continuously mixed on line and a recyclable emulsion-associating fracturing fluid system that can be mixed with surface water and hot sewage were developed, which can effectively ensure the fracturing fluid preparation and water source for large-scale continuous fracturing operations. Moreover, the well-plant operation mode and fracture monitoring technique were upgraded. The proposed technology has been successfully applied in tight oil blocks such as Y227, Y22 and Y104. By greatly improving the single-well productivity and lifecycle, it helps increase the development benefit. Accordingly, the utilization degree of the tight oil in Shengli oil field has been improved economically and effectively.

Mahu tight conglomerate reservoirs have huge potential of tight oil resource and exploitation. Based on the complex reservoir-forming conditions, poor reservoirs property, strong heterogeneity and large sand body span, hydraulic fracturing in this area was facing serious challenges in fracture initiation and proppant placement. Annual production capacity of fractured wells were under expectation. According to the concept of "fracture-controlled reserves", series technologies of subdivision volume fracturing are integrated after 5 years of exploration. High-efficiency initiation and extension of multi-cluster fractures in one section are achieved by using drillability bridge plug segmented, small crack spacing cluster perforation and large displacement inverse mixing injection technologies. The effect of proppant placement and reservoir pressure are improved through multi-scale proppant adding method and increasing the dosage of slippery water to replace the guar gum. The series technologies have been widely applied in 11 blocks and 86 wells in Mahu, including exploration, evaluation and development area. For tight oil reservoir, the fracturing and producing effects have improved and economic development has been realized. Then, development of the total Mahu oilfield is effectively promoted.

Partitioned volume fracturing has been applied in 118 wells in 11 tight conglomerate reservoirs in Mahu oilfield, proving the technique's suitability and operability. However, the best matching between rational fracturing parameters and optimal production results is still uncertain. In order to define the rational engineering technical parameters to guide the subsequent horizontal well fracturing design and also improve the comprehensive benefits of tight conglomerate reservoir development, the adaptability of horizontal well volume fracturing was studied through correlating the production data (e.g., post-fracturing production and pressure) to the fracturing engineering parameters (e.g., volume fracturing method, completion fracturing process, fracture parameters, fracturing scale and fracturing materials). The results show that the rational fracture spacing, sanding rate and sand-to-liquid ratio are 25-35 m, 1.2-1.5 m³/m, and 1:17-1:20 respectively for normal pressure reservoirs with poor physical properties, and about 40 m, 1.0-1.2 m³/m, and 1:15-1:17 respectively for abnormally high-pressure reservoirs with good physical properties. In addition, it is proved that precise fixed-point and controlled fracturing stimulation can increase post-fracturing production by more than 20% under the same conditions. In the block where the reservoir depth is less than 3500 m and the closing stress is lower than 55 MPa, quartz sand can effectively replace ceramsite, so it is promising for wider application.

In Block Ma 56 of the Santanghu Basin, a large quantity of tight oil in place remains unrecovered after stimulated by horizontal well volume fracturing, suggesting an overall recovery of only 3%. A considerable volume of remaining oil near wells and in fractures can be developed. In order to further improve the single-well productivity and recovery, the practices of volume fracturing of tight oil reservoirs around the world were reviewed. On this basis, a technology of densely-spaced wells + partitioned volume fracturing was proposed under the guidance of geological and engineering integration, that is, the densities of both well pattern and induced fractures are increased to ensure the wellbore and fracture system to cover all reserves in the reservoir, so that the reservoir productivity can be maximized. Moreover, five supporting techniques were developed, i.e. well infilling, long horizontal section drilling, partitioned and staggered fracture initiation, water injection, and low-cost volume fracturing. Application in 41 wells shows the effective rate is up to 100%, the average daily oil production per well is 26.2 tons, and the cumulative oil production increases by 39.7%. The technology is helpful to improving single-well productivity and recovery of tight reservoirs in Block Ma 56.