Production Calculation Model of Thermal Recovery after Hydraulic Fracturing and Packing in Tight Reservoir

It was deemed important to calculate the thermal recovery production model of tight oil reservoirs after fracturing and packing based on the field data of an oilfield in Bohai Sea, China. The thermal recovery production of a tight oil reservoir after fracturing is demonstrated through theoretical calculation and practical field data on the premise of five hypotheses. Fractures change the fluid flow capacity of the reservoir. Combined with the relevant theories of reservoir thermal production, the dual porosity system in the fractured zone and the single porosity system in the unfractured zone were established. The calculation models of heat loss in the fractured and unfractured zones were derived to determine the thermal recovery heating radius of the reservoir after fracturing and packing. Combined with the pseudo-steady state productivity formula of the composite reservoir, a production calculation model of thermal recovery after fracturing and packing in the tight oil reservoir was established. The results showed that the heating radius of the reservoir after fracturing and packing is smaller than that of the unfractured reservoir, and the additional heat absorption of the fracture system generated by fracturing and packing reduces the thermal recovery effect. The thermal recovery productivity of heavy oil reservoirs is mainly affected by the heating radius. With the increase of fracture density, the heating radius decreases and production decreases. The increase of fracture porosity also leads to the decrease of the heating radius and the production. The calculation result of this model is improved after tight oil reservoir fracturing during the production period, which indicates that the model has a better prediction effect of the production of the tight reservoir after fracturing and packing.

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Simulation and Optimization of CO2 Huff-n-Puff Processes in Tight Oil Reservoir: A Case Study of Chang-7 Tight Oil Reservoirs in Ordos Basin

10.2118/191873-ms ◽

2018 ◽

Cited By ~ 1

Author(s):

Zhengdong Lei ◽

Shuhong Wu ◽

Tao Yu ◽

Yi Ping ◽

He Qin ◽

...

Keyword(s):

Ordos Basin ◽

Oil Reservoirs ◽

Tight Oil ◽

Oil Reservoir ◽

Simulation And Optimization ◽

Tight Oil Reservoir ◽

Tight Oil Reservoirs

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Characteristics and origin of the pore structure of the lacustrine tight oil reservoir in the northwestern Jiuquan Basin, China

Interpretation ◽

10.1190/int-2018-0108.1 ◽

2019 ◽

Vol 7 (3) ◽

pp. T625-T636

Author(s):

Chunyan Fan ◽

Xianglu Tang ◽

Yuanyin Zhang ◽

Yan Song ◽

Zhenxue Jiang ◽

...

Keyword(s):

Pore Structure ◽

Oil Reservoirs ◽

Tight Oil ◽

Oil Reservoir ◽

Type I ◽

Thin Sections ◽

Tectonic Events ◽

Tight Oil Reservoir ◽

Tight Oil Reservoirs ◽

Intercrystalline Pores

The pore structure controls the formation processes of tight oil reservoirs. It is meaningful to study the characteristics and origin of the pore structure of the tight oil reservoir. We have analyzed the pore structure of the tight oil reservoir by thin sections, scanning electron microscopy, and mercury intrusion porosimetry. We analyze the origin of the pore structure based on sedimentological, diagenetic, and tectonism processes. The porosity of the tight oil reservoirs is mainly approximately 2%–10%, and the permeability is mainly from 0.01 to 0.3 mD. The pores of the lacustrine tight oil reservoir can be classified into the primary pore and the secondary pore. The main pores are matrix micropores and clay intercrystalline pores, as well as a few dissolved pores. However, the primary residual intergranular pore has almost disappeared, leading to a poor connectivity with a general size between 20 and 50 μm. The pore throat is divided into three categories (type I, type II, and type III) according to the porosity, permeability, and throat size and distribution. We determine that the pore structure of the lacustrine tight oil reservoir is related to sedimentary, diagenetic processes, and later tectonic events. The compaction and cementation are the main factors, whereas the dissolution and tectonic events have minor effects.

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New Method Research of Tight Oil Reservoir Pulse Decay Permeability Measurement

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1010-1012.1768 ◽

2014 ◽

Vol 1010-1012 ◽

pp. 1768-1771

Author(s):

Hai Yang Qu ◽

Zheng Ming Yang ◽

Ting Hu

Keyword(s):

Steady State ◽

Oil Reservoirs ◽

New Method ◽

Test Accuracy ◽

Tight Oil ◽

Oil Reservoir ◽

Permeability Measurement ◽

Good Relationship ◽

Tight Oil Reservoir ◽

Tight Oil Reservoirs

The permeability of tight oil reservoir is very low and general perm-plug method always has a big difference. The results can’t reach the test accuracy requirements. This paper measured 26 block rocks of Changqing tight oil reservoir and several typical tight oil reservoirs in CNPC with pulse decay new method. The result shows that the pulse decay permeability measured in the new method and steady-state Klinkenberg-corrected permeability have a good relationship. We drew a figure about the porosity and steady-state Klinkenberg-corrected permeability of these tight oil reservoirs. This research offers a technical support to the tight oil reservoirs about basic data permeability measurement.

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Optimization of Gas Channel Controlling Technique During Co2 Immiscible Flooding in Normal Pressure Tight Oil Reservoir——A Case Study of Honghe Chang 8 Reservoir in South Ordos Basin

10.2523/iptc-21334-ms ◽

2021 ◽

Author(s):

Ting Xu ◽

Yi Wei

Keyword(s):

Large Scale ◽

Normal Pressure ◽

Small Scale ◽

Tight Oil ◽

Oil Reservoir ◽

Co2 Flooding ◽

Tight Reservoir ◽

Starch Gel ◽

Tight Oil Reservoir ◽

Gas Channeling

Abstract Tight oil reservoir is commonly recognized to be difficult to supply the formation energy. Tight oil reservoir in Ordos basin is characterized to be continental sedimentation, strong heterogeneity, normal pressure (0.9), low reserve abundance, imperative to supply the displacing energy. CO2 have good injection and high displacing efficiency for extra-low permeability reservoir, which provides the reference for exploring the effective development mode in tight reservoir. Influencing by complex fracture and hydraulic fracturing, as CO2 flooding is conducted in tight oil reservoir, gas channeling phenomenon is very serious, displacing energy is difficult to be utilized. To enlarge CO2 sweep efficiency, how we can effectively control CO2 channeling becomes the first important issue in energy supplying development of normal pressure tight reservoir. In the paper, a case of Honghe Chang 8 tight oil reservoir was carried out. Medium-large and medium-small scale fractures were artificial fabricated in natural crop cores according to G&G understanding. In different fracture openings models, two-stage blocking experiments with CO2 flooding were operated with high-strength starch gel and weak-strength ethylenediamine. Slug combination, volume and sequence were evaluated and by numerical simulation, blocking strength were defined to reflect the plugging effect in the experiment. Then build up well group numerical simulation model, characterizing the complex fracture network. Blocking sites and volume of plugging agents were analyzed and optimized. Two-stage blocking technique was determined in the fracture developed tight reservoir during CO2 flooding. Research results indicate it is priority to control the gas channeling of medium-large scale fractures with sufficient volume of the starch gel. As CO2 flooding is performed, gas starts to break through, followed by small volume ethylenediamine to mitigate gas channeling. Numerical simulation shows that firstly fully controlling gas channeling from medium-large scale fracture along with principal stress, then injecting plugging agent from the injection well, being located in 1/3~1/2 of well space to treat medium-small scale fractures with the best production stimulation. Starch gel volume is determined by medium-large scale fractures pore volume(PV), while low concentration starch gel and ethylenediamine volume is optimized to be half of the medium-small scale fracture PV, in which PV of fracture permeability lower than 200×10-3μm2 determine ethylenediamine volume. Generally, plugging agent would be more than 1500m3 for a pair of I-P wells. With low cost CO2 source, CO2 flooding is expected to be one of the important development modes for normal pressure tight oil reservoir. During CO2 immiscible flooding, gas channel controlling technique plays decisive roles in ensuring successful development. Research results are not only advisable for the Ordos normal pressure tight reservoir development, but also for the similar tight reservoir in the world.

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OVERALL PSD AND FRACTAL CHARACTERISTICS OF TIGHT OIL RESERVOIRS: A CASE STUDY OF LUCAOGOU FORMATION IN JUNGGAR BASIN, CHINA

Fractals ◽

10.1142/s0218348x1940005x ◽

2019 ◽

Vol 27 (01) ◽

pp. 1940005 ◽

Cited By ~ 5

Author(s):

XIXIN WANG ◽

JIAGEN HOU ◽

YUMING LIU ◽

PEIQIANG ZHAO ◽

KE MA ◽

...

Keyword(s):

Fractal Dimension ◽

Pore Radius ◽

Junggar Basin ◽

Oil Reservoirs ◽

Tight Oil ◽

Oil Reservoir ◽

Mercury Injection ◽

Fractal Characteristics ◽

Tight Oil Reservoir ◽

Tight Oil Reservoirs

Lucaogou tight oil reservoir, located in the Junggar Basin, Northwest of China, is one of the typical tight oil reservoirs. Complex lithology leads to a wide pore size distribution (PSD), ranging from several nanometers to hundreds of micrometers. To better understand PSD and fractal features of Lucaogou tight oil reservoir, the experiment methods including scanning electron microscope (SEM), rate-controlled mercury injection (RMI) and pressure-controlled mercury injection (PMI) were performed on the six samples with different lithology. The results indicate that four types of pores exist in Lucaogou tight oil reservoir, including dissolution pores, clay dominated pores, microfractures and inter-granular pores. A combination of PMI and RMI was proposed to calculate the overall PSD of tight oil reservoirs, the overall pore radius of Lucaogou tight oil reservoir ranges from 3.6[Formula: see text]nm to 500[Formula: see text][Formula: see text]m. The fractal analysis was carried out based on the PMI data. Fractal dimension (Fd) values varied between 2.843 and 2.913 with a mean value of 2.88. Fd increases with a decrease of quartz content and an increase of clay mineral content. Samples from tight oil reservoirs with smaller average pore radius have stronger complexity of pore structure. Fractal dimension shows negative correlations with porosity and permeability. In addition, fractal characteristics of different tight reservoirs were compared and analyzed.

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Tight oil reservoir production characteristics developed by CO2 huff ‘n’ puff under well pattern conditions

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-021-01446-1 ◽

2022 ◽

Author(s):

Zhizeng Xia ◽

Xuewu Wang ◽

Rui Xu ◽

Weiwei Ren

Keyword(s):

Physical Properties ◽

Oil Recovery ◽

Oil Reservoirs ◽

Injection Timing ◽

Tight Oil ◽

Oil Reservoir ◽

Natural Energy ◽

Tight Oil Reservoir ◽

Tight Oil Reservoirs ◽

Production Characteristics

AbstractTight oil reservoirs have poor physical properties, and the problems including rapid oil rate decline and low oil recovery degree are quite common after volume fracturing. To obtain a general understanding of tight oil reservoir production improvement by CO2 huff ‘n’ puff, the high-pressure physical properties of typical tight oil samples are measured. Combining the typical reservoir parameters, the production characteristics of the tight oil reservoir developed by the CO2 huff ‘n’ puff are numerically studied on the basis of highly fitted experimental results. The results show that: (1) during the natural depletion stage, the oil production rate decreases rapidly and the oil recovery degree is low because of the decrease in oil displacement energy and the increase in fluid seepage resistance. (2) CO2 huff ‘n’ puff can improve the development effect of tight oil reservoirs by supplementing reservoir energy and improving oil mobility, but the development effect gradually worsens with increasing cycle number. (3) The earlier the CO2 injection timing is, the better the development effect of the tight reservoir is, but the less sufficient natural energy utilization is. When carrying out CO2 stimulation, full use should be made of the natural energy, and the appropriate injection timing should be determined by comprehensively considering the formation-saturation pressure difference and oil production rate. The research results are helpful for strengthening the understanding of the production characteristics of tight oil reservoirs developed by CO2 huff ‘n’ puff.

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