Study On Cementing System Of Shale Gas Horizontal Well Cementing

Shale gas exploitation need for perforating and large-scale fracturing downhole operations, conventional cement under the impact of perforations and huge loads of casing pressure, could easily lead to failure of the packer integrity of cement. Therefore, it proposed new challenges for shale gas cementing techniques. Combined casing-cement-formation coupled mechanical model to calculate the cement sheath mechanical deformation under different downhole conditions, and micro-annul us occurs the distribution of the different cement elastic modulus corresponding to maximum wellhead pressure. Proposing mechanical performance requirements for the packer integrity of shale gas horizontal well cement. Through experiment preferred horizontal well of shale gas additional cementing materials, including:elastic and toughness materials, bulking agents, suspension stabilizer, self-healing agent. In laboratory experiments, Regular performance evaluation from the slurry, expansion properties, channeling properties, mechanical properties and conventional triaxial mechanical experiments, forming a elastic and toughness cement slurry system to meet the mechanical performance requirements for shale gas horizontal well cement. This paper’s main research work and results are as follows:1. Combined with casing-cement-formation coupled elastic model, launched a wellhead pressure changes and different elastic modulus cement for cement mechanical deformation studies, and micro-annulus occurs the distribution of the different cement elastic modulus corresponding wellhead pressure. Proposing the mechanical performance requirements for shale gas horizontal well cement:fracturing while wellhead pressure does not exceed50MPa, cement elastic limit stress is greater than14.36MPa, ultimate strain is greater than0.262%.2. Optimizing cement additive materials to improve the mechanical properties:latex, elastic particles and polypropylene fibers. Determine the scope of the initial amount plus additional material, Latex:0～15%, the elastic particles:0～6%, polypropylene fibers:0～1%3. Based on the cementing property requirement of cement, choosing the expansive BS500to improve expansion performance, and adding micro silica to improve suspension stability, choosing self-healing experiments CEM-2to extend the life of shale gas wells.4. According to the optimized elastic and toughness materials and the added amount, carried out the experimental analysis for single and compound forms elastic and toughness cement slurry. Thus, concludes latex、elastic particles could reduce elastic limit stress for the elastic modulus of cement slurry contrast with the fiber,affected little on elastic modulus, can improve the stress and ultimate strain. The thesis carries on the rational of ductile material combination in order to reduce the cement elastic modulus and enhance cement elastic limit stress and elastic strain limit. As result the cement mechanical deformation capacity get improved. 5. Based on comprehensive performance analysis of single handed and compound forms elastic and toughness materials, combined with regular cement additives, aiming to get formula slurry system adapted to shale gas horizontal well application debris mechanical performance requirements is following:basic formula+(9%-12%)latex+(2%-4%)elastic particles+0.5%fiber.6. According to preferred CEM-2, adding the self-healing agent in the preferred formulations can improve cement that produced micro-cracks, and the underground micro annulus packer integrity.