## 1 Introduction  
Steam conformance is a key factor in steam-based recovery processes of heavy oil reservoirs [1; 2; 3; 4; 5]. Due to different sedimentation backgrounds in the formation, different sedimentation results in different rock types and properties, and the difference in lithology causes the reservoir heterogeneity. Meanwhile, the CSS process of vertical wells always needs to inject a large amount of steam into the payzone during a limited period, which requires an injection speed of normally more than 80 m\({}^{3}\)/d(CWE). Fast injection with high pressure and high temperature tends to creep the oil sand and leads to mini-fractures in high-permeability zones [6; 7]. It has been found that multi-cycles of steam injection extend the fractures with steam and the reservoir heterogeneity deteriorates. Extensive studies have been carried out to understand the reservoir heterogeneity, both for lithology and rock mechanics. Moreover, the literature has proposed some useful strategies to improve the steam conformance, such as high-temperature gas foam with steam [8; 9], an oil viscosity reducer or solvent to increase the injection capacity and reduce the fractures [10; 11; 12], and thermoreversible gel to plug the steam channels [13]. Polymer gels are potential plug agents to solve near wellbore issues. Researchers have found a new HPAM gel formula that could be stable for more than 7 days at 175 \({}^{\circ}\)C, while a co-polymer with heat resistance groups was found to improve the applied temperature to 200 \({}^{\circ}\)C. Filed applications in four vertical wells and one horizontal well have demonstratedthat the gel plugs are applicable in a wide range of wellbore temperatures, from 60 \({}^{\circ}\)C to 191 \({}^{\circ}\)C [14]. Moreover, a review article discussed polymer gel techniques from innovations to applications. The development of polymer gels to resist temperature, early gel formation, synergistic mechanisms and influence of pH, and high salinity is the future trend to meet harsh reservoir conditions [15]. Other researchers have proposed that an oil-in-water (O/W) emulsion could be an innovative conformance control technology due to its strong plugging ability [16]. They used parallel-sandpack flow tests with the permeability ratios of 4:1 and 5:1 to investigate the performance of conformance control by O/W emulsion injection. They found that a carefully designed O/W emulsion of droplets can deform and migrate deeply into both the high permeability sandpack and the low permeability sandpack, leading to an ideal fractional flow ratio (0.5:0.5) and achieving a good conformance control in the parallel-sandpack model. FCD/ICD is also an effective downhole tool to improve the distribution of steam in the wellbore [17; 18], while it only takes effect in allocating the steam in the wellbore, which is effective at the early production stage, while ineffective at the late production stage as the steam tends to redistribute and converge in the inter-well region. The well configuration and well pattern can be modified to change the streamline of injected fluid [19; 20], while the systematic workover requires a substantial operational cost and the valid period is unknown. Parameters can be optimized for integral wells' management [21; 22], but for wells in harsh reservoir conditions or those with severe steam channeling problems, the alteration of operational parameters can hardly take effect due to the preferential streamlines of steam in porous media. For wells with no further oil recovery potential, they can be converted to other follow-up recovery methods [23]. The evolution of heterogeneity and its fundamental impacts on steam conformance and liquid production rate for different permeability and heterogeneity levels in the process of steam injection has not been fully understood, and the steam profile control strategies after steam channeling and the well-to-well fracture communication need to be optimized.